Baron Carl Claus von der Decken - 1833-1865 - Collectors in East Africa - 31.

By Bernard Verdcourt

Text extracted from The Conchologists’ Newsletter, No.162, pp. 204–211 published September 2002. Image courtesy of Wikipedia.
Carl Claus von der DeckenCarl Claus von der Decken was born on 8 August 1833, at ‘Kotzen in the Mark’ (presumably the one 30 km N. of Brandenburg) the youngest son of Baron Ernst von der Decken, one of an old and wealthy Bavarian family. Ernst had been an officer in the English Legion and fought at Waterloo and later became Equerry and Master of Horse in Hanover to three kings of Great Britain, George III, George IV and William IV who were also Kings of Hanover from 1815–1837, after which the dual role ceased since Queen Victoria, as a woman, was ineligible. George Ill, also George I and George II, had been Electors of Hanover before 1815. The throne passed to the Duke of Cumberland, Ernest Augustus (1771–1851) and Baron Ernst served him also. Carl Claus’s mother was a daughter of a Prussian, Colonel Friedrich von Stechow.

Not surprisingly Claus joined the army at eighteen but spent much of his time studying mathematics, languages, zoology and botany. He travelled extensively in Europe and in 1858 went game shooting in Algeria but he had long wanted to become an explorer. On his return to Hanover the same year he left the army.

He soon had the opportunity to join (and finance) the expedition to East Africa of Dr Albrecht Roscher (?1836–1859) (after whom the very attractive orchid Vanilla roscheri Reichb. f. is named). Roscher had in fact already left for Zanzibar and a journey down the coast to Mozambique; by February 1859 he was just north of Dar es Salaam where he met Burton and Speke (Burton, 1872 ii: 332). He reached Mozambique in March but sadly was murdered by Lake Nyasa (Gray, 1958).

Claus arrived in Zanzibar in September 1860 and found out about the murder and set about trying to organise a journey to rescue Roscher’s effects and avenge his murder. The perpetrator had actually already been beheaded. When Claus arrived in Kilwa after sailing down the coast he found everything possible was done to thwart him continuing. After a further 165 miles he gave up and returned to Zanzibar. He gave up the idea of exploring Lake Nyasa and decided to visit Kilimanjaro and Kenya. On 28 May 1861 accompanied by Koralli (a European companion who had nearly died on the journey beyond Kilwa) and by Richard Thornton (Note 1) (1838–1863) Claus crossed to Mombasa and met the missionary Johann Rebmann (1820–1876) at Rabai. He reached Kilimanjaro six weeks later but was only able to reach 2400 m. At least he could confirm the mountain was covered in snow which many in Europe had said was impossible (now 140 years later the snow is receding at an alarming rate). He returned to Mombasa via the Usambaras, the Umba R. and Vanga; after visiting Takaungu he sailed for Zanzibar calling in at Pangani on the way. On arrival in Zanzibar Thornton left but Claus stayed on Zanzibar from November 1861 until August 1862 waiting for an assistant Dr Otto Kersten (1839–1900) and a hunter named Androk. Whilst waiting he investigated the history, geography, geology, zoology and botany of the island (von der Decken, 1869–79). A new attempt was made on Kilimanjaro and they reached 4200 m, but an attempt to proceed towards Lake Victoria was blocked by Masai and they arrived back in Zanzibar on 30 December 1862. He then had the idea that one could reach Mt Kenya by taking a paddle-steamer up one of the rivers reaching the east coast north of Mombasa. He ordered a boat from Europe and in the meantime decided to visit the Comoro and Seychelle islands, Reunion, Mauritius and Madagascar. Koralli, his companion and servant died in Reunion and Madagascar was in such a state of unrest that he could not leave the coast.

Since no boat of the size he needed could be found he returned to Europe to supervise the building of one himself, arriving in Hanover in September 1863. He was acclaimed in all the major European capitals and in London received the Gold Medal of the Royal Geographical Society. He made arrangements in Hamburg for the construction of a paddle-steamer the Welf (cub or whelp) and a steam-launch Passe partout. His old friend Count van Goetzen offered to join him and they engaged a staff, two from the Austrian Navy, a doctor, an artist, two mechanics, a carpenter and a cook. Both boats (in bits), von der Decken, Goetzen, the staff and all the stores including 300 tons of coal arrived in Zanzibar in November 1864 where they were received by Kersten who had arrived earlier. The boats were assembled on the sea front at Zanzibar, the steam-launch being ready in February 1865. Claus used it to explore the estuaries of the R. Tana and R. Ozi which used to join about five miles inland. Later in June the Welf was launched and flew the Hanoverian flag. At this stage Kersten and Goetzen, both ill, had to return to Europe. For over 200 years the diseases in Africa had been sorting out those Europeans who could cope from those who could not. Some died within a few weeks of arrival; others survived despite catching the diseases, others seemed to be immune to everything. Quinine and other drugs of course soon made it safer for all. East Africa was a healthier place than West Africa; in fact the highlands were one of the healthiest places in the world.

From Lamu both boats proceeded to the Tula R. escorted by HMS Lyra. Then everything began to go wrong. Cholera struck and eight men died but Claus survived. On 29 July the boats left for the Juba R.; the Welf ran ashore but was refloated. The Passe partout was wrecked on the rocks and its mechanic drowned. Claus pressed on and after a month arrived at Bardera 165 miles from the mouth; after a week he moved on but 20 miles further on the Welf was also wrecked and the remains were still visible in the 1920s and might possibly be there still. Claus now decided to proceed on foot but had to return to Bardera to obtain provisions. He travelled with Dr Link (1839–1865) (Note 2) the medical doctor attached to the expedition and interestingly Mabruki Speke who had travelled with Speke. On 1st October the rest of the camp was attacked (little seems to have changed in Somalia!) and Brenner, the only one properly armed shot the marauders. Only five Europeans remained and they returned to the coast rowing. They actually passed Claus’s boat without stopping, fearing the worst, reached the coast in five days and arrived in Lamu on 16 October and finally Zanzibar on 24 October. On 15 November Mabruki arrived at Lamu from Brava (Barawa) and reported that von der Decken and Link had been murdered on 2 October.

The publication of von der Decken’s results and the account of the journey was entrusted to Otto Kersten by Claus’s mother Princess Adelheid of Pless (she had remarried after Ernst’s death, Prince Hans Henry X of Pless) then to Baron Julius von der Decken after her death. The full results of the journey were not completely published for many years. Many new plants and animals were described from the collections made. Everyone who has travelled in the East African bush will know the call of von der Decken’s hornbill, Tockus deckeni (Cabanis). One of the most spectacular alpine plants in the world is Lobelia deckenii (Aschers.) Hemsl. a fitting memorial to this explorer who is scarcely mentioned in English books on African exploration.


List of molluscs described from material collected during the von der Drecken expedition

Ampullaria ovata Ol. var. deckenivon Mts., 1897.   Without locality but certainly Zanzibar I. or Zanzibar coast on mainland, von der Decken exp. (type material: ZMB); Zanzibar I. Mwera-Brücke, Stuhlmann (type material: ZMB); swamps N. and S. of Bagamoyo, Stuhlmann (type material: ZMB); Pangani, Schmidt (type material: ZMB); Usaamo, Mengwe-Teich, Stuhlmann(type material: ZMB).
Pila ovata (Ol.) (Note 3)
Buliminus rhodtaenia von Mts., 1869.   Kenya, without exact locality but probably area near Tana R. (holotype: ZMB 15258, see Kilias (1971: 230)).
Rhachistia rhodotaenia (von Mts.).
Helicarion aureofuscus von Mts., 1869a.   Kenya, Mombasa (‘Mombas’) (type material: ZMB). Nothing like this has been refound – shell has shape of a Mesafricarion (see Note 4).
Nanina mozambicensis (Pfr.) (as ‘mossambicensis’ var. albopicta von Mts., 1869a.   East Africa, without precise locality (type material: ZMB).
Trochonanina mozembicensis albopicta (von Mts.).
Nanina pyramidea von Mts., 1869a.   Kenya, Mombasa (‘Mombas’) (type material: ZMB)
Trochonanina pyramidea (von Mts.).
Parmarion kerstenii von Mts., 1869a.   Between Zanzibar and Cape Delgado (holotype: ZMB 17644, see Kilias 1974: 348, fig.2).
? Succinea (Note 5).
Physa seychellana von Mts., 1869a.   Seychelles (type material: ZMB 95962 lectotype: 9596b, 15 paralectotypes: see Kilias (1961:161).).
Physa acuta (Drap.) (= Physa borbonica Fér.) (See Starmühlner, 1983).

Von Martens (1869b) described some snails found in bags of sesame seed which had been sent to W. Brauns, a factory owner, in Goslar, Hanover. Since some of these were also described in von Martens (1869a) it seems reasonable to deal with them here (see Note 6). Von Martens pointed out in the paper that Sesamum was very widely grown on Zanzibar I. and on the mainland coastal strip, which was also called Zanzibar, so it is not certain from which the shells (both land and marine) mixed with the seed originated, since the coastal produce would also have been sent to Zanzibar for final export to Europe.


List of molluscs described from material found in bags of sesame seed sent to Germany from Zanzibar

Buliminus braunsii von Mts., 1869a, b.   Zanzibar, found amongst sesame seed, W. Brauns (lectotype: ZMB 18005b selected by Kilias (1971:218, fig. 2); 9 paralectypes ZMB 18005b).
Rhachidina braunsii (von Mts.) (see Note 7).
Buliminus braunsii von Mts. var. lunulatus von Mts., 1897.   Zanzibar, found amongst sesame seed, W. Brauns (two paralectotypes: ZMB 18005c); Tanzania, between Tanga and Mbessa, Conradt (lectotype, ZMB 44716 (see Kilias (1971: 226)); other syntypes were Usegua, W. Schmidt (ZMB) and between Lake Nyassa and the east coast, Thomson (BM).
Rhachidina braunsii lunulata (von Mts.)
Buliminus braunsii von Mts. var. hypostictus von Mts., 1897.   Zanzibar, found amongst sesame seed, W. Brauns (lectotype: ZMB 18005d, see Kilias (1971:223–224, fig. 6)); Kinga, St. Paul (2 paralectotypes, ZMB 101598); Zanzibar I., var. Dr. Kobelt erhalten (2 paralectotypes ZMB 101588); between Lake Nyassa and the east coast, Thomson (syntype, BM).
Rhachidina braunsii hyposticta (von Mts.)
Buliminus conulinus von Mts., 1869a, b.   Zanzibar, found amongst sesame seed, W. Brauns (holotype: ZMB 18008)
Edouardia conulina (von Mts.).
Ennea laevigata Dohrn var. sexdentata von Mts., 1869b.   Zanzibar, found amongst sesame seed, W. Brauns (type material: ZMB)
Gulella sexdentata (von Mts.).
Nanina plicatula von Mts., 1869a, b.   Zanzibar, found amongst sesame seed, W. Brauns (type material: ZMB; see Vercourt (1960)).
Trochonanina plicatula (von Mts.).


1.    Thornton, a mining geologist, had previously been with Livingstone and Kirk on the Zambesi Expedition but left them. Later he rejoined them on the Zambesi and died there a few days before his 25th. birthday.
2.    L.J. Dorr (1997) spells the name Linck and gives some information about him. Hermann Albert (‘Albert-Armand’) Linck was an assistant surgeon-major in the Prussian Army and is also described as a zoologist.
3.    Pain (1961) sinks var. deckeni into Pila adusta (Reeve) and von Martens originally included Reeve’s name with a query under his var. deckeni. Brown (1994) treats adusta as a synonym of ovata.
4.    As I have pointed out (Verdcourt, 2000) Mombasa is a virtually impossible locality for a urocyclid of the Chlamydarion assemblage and relatives. None has been found on the coast nor have I seen any from the Usambaras, Ulugurus etc. The only place visited by the expedition from which a species is known is Kilimanjaro. The shape is reminiscent of a Mesafricarion.
5.    Van Goethem does not mention this name in his revision of Urocyclid slugs (1977) nor do Forcart, Simroth or Verdcourt in papers on slugs. Kilias lists it under Succinea.
6.    I have been unable to establish which of von Martens’s 1869 publications appeared first. Kersten’s forward to volume 3 of von der Decken’s Reisen is dated August 1869, Altenburg, and even making allowance for the amazing efficiency of those days surely could not have appeared the same month or perhaps Kersten dated his preface knowing when it would appear. The paper in the Nachrichtsblatt appeared in part 10 of volume 1 which also appeared in August. The fact that von Martens refers in this paper to his work in the Reisen does not necessarily mean it appeared first but that he had page proofs of it. The mollusca from sesame seeds are partly described twice, once in the Nachrichtsblatt paper and also in the Reisen on p. ‘160’, the same page as Parmarion kerstenii. There is a fault in the pagination of the Reisen (at least in the copy I examined) – the pages run 158, 150, an unnumbered (= 160).
7.    In both 1869 papers von Martens spelt braunsii with two ii but in 1897 with only one.



Brown, D., 1994.     Freshwater snails of Africa and their medical importance, ed. 2. London.
Burton, R., 1872.     Zanzibar; City, Island, and Coast. 2 vols., London.
Dorr, L.J., 1997.     Plant collectors in Madagascar and the Comoro Islands. Kew.
Gray, J., 1958.     Albrecht Roscher. Tanganyika Notes Rec. 50: 71–84.
Hollis, C., 1958.     Von der Decken. Tanganyika Notes Rec. 50: 63–67 (reprinted from a Zanzibar government pamphlet).
Kilias, R., 1971.     Die Typen und Typoide der Mollusken Sammlung des Zoologischen Museums in Berlin (6) II. Euthyneura, Stylommatophora, Orthurethra, Pupillacea (Enidae). Mitt. zool. Mus. Berl. 47 (1): 215–238, 10 figs.
Kilias, R., 1974.     Die Typen und Typoide der Mollusken Sammlung des Zoologischen Museums in Berlin (7) II. Euthyneura, Stylommatophora, Heterurethra, Succineacea (Succineidae) und Athoracophorea (Athoracophoridae). Mitt. zool. Mus. Berl. 49 (2): 345–350, 2 figs.
Martens, E. von, 1869a.     Mollusken, pp. 55–66, tt. 1–3; Seesterne und Seeigel pp. 123–134; Uebersicht der ostafrikanischen Süsswasserfische pp. 141–144; Uebersicht der Land und Süsswassermollusken der ostafrikanischen Küste von Cap Guardafui bis Port Natal nebst den nächtstliegenden Inseln pp. 140–160. In O. Kersten ed. Baron Carl Claus von der Decken’s Reisen in Ost-Afrika in Jahren 1859–1865. Vol.3, Wissenschaftliche Ergebnisse, part 1, Säugethiere, Vogel, Amphibien, Crustaceen, Mollusken und Echinodermen. Leipzig and Heidelberg, C.F. Winter’sche, pp. xii + 169, tt. 35.
Martens, E. von, 1869b.     Conchylien aus Zanzibar zwischen Sesamssamen. NachrBl. Dt. Malakozool. Ges. 1 (10): 149–156.
Martens, e. von, 1897.     ‘Beschalte Weichthiere’ in Möbius, Deutsch Ost-Afrika 4, Abt. 1. Berlin.
Pain, T., 1961.     Revision of the African Ampullariidae; species of the genus Pila Röding 1798. Annls. Mus. r. Afr. centr., sér. 8º, Sci. Zool. No. 96.
Starmühlner, F., 1983.     Results of the Hydrobiological Mission 1974 …… Vienna. Part VIII. Contributions …… Indian Ocean Islands. Annln. naturhist. Mus. Wien. 84B: 127–249.
Van Goethem, J.L., 1977.     Révision systematique Urocyclinae (Mollusca, Pulmonata, Urocyclidae) Annls. Mus. r. Afr. centr., sér. 8º, Sci. Zool. No. 218.
Verdcourt, B., 1960.     some further records of Mollusca from N. Kenya, Ethiopia, Somaliland and Arabia, mostly from arid areas. Rev. Zool. Bot. afr. 61: 221–265.
Verdcourt, B., 2000.     Mollusca, in Burgess, N.D. & Clarke, G.P., Coastal Forests of Eastern Africa, 219–224, 413–415.


Since this article was set up I have, through the kindness of Dr Matthias Glaubrecht, of the Museum für Naturkunde, Berlin, been able to see the types of Physa seychellana and Parmarion kerstenii; a search for material of Helicarion aureofuscus proved unsuccessful. The material of Parmarion kerstenii has been labelled Hyalimax kerstenii and this seems to be the correct disposition. No other material has turned up on the East African coast. The flattened shell, about 7.5 mm long, resembles a miniature Ostrea edulis valve in shape but is closely concentrically striate and quite characteristic. H.E. Quick gives a full account of a Mauritian species (see Mauritius Inst. Bull. 1(5): 57–62 (1939)).

B. Verdcourt