The Freshwater Molluscs of Northern Africa; Distribution, Biogeography and Palaeoecology

Ever since the monumental work of Pilsbry and Bequaert (1927) with its quite remarkable coverage of published names of African freshwater molluscs, still an unsurpassed tool, this group has been rather well-served with literature, at least by comparison with the land molluscs. Mandahl-Barth's book on the Uganda fauna and many revisionary papers, further revisions and popular leaflets from the Danish Bilharziasis Laboratory and particularly David Brown's recent manual have made identification of freshwater molluscs possible. This literature is of course basically due to the importance of water-snails in transmitting various diseases. However, most of it omits the species of that part of Africa falling within the Palaearctic region; the same area is also not dealt with in works devoted to the Mediterranean area. Van Damme's book, volume 25 in a general series 'Developments in Hydrobiology' fulfils a real need and complements the other works, particularly as it includes coverage of the bivalves, not treated in Brown's work. The emphasis of the book is the geologically recent history of the Sahara and the value of molluscan studies in understanding its fascinating climatic vicissitudes; it does, however, cover a much more extensive field.

A brief history of collecting in northern Africa as a whole precedes the main treatment and as usual Bourguignat has complicated matters by excessive splitting. Pallary following later emulated him to no small extent. Part one occupies over half the book and is a review of the species, a compilation and not a revision which in some groups e.g. Hydrobiidae is much-needed. Species in 49 genera are dealt with. The descriptions are brief but line drawings are given of each. These are adequate save in the case of Pisidium where the hinge details could be clearer. Fig. 112 purporting to depict Sphaerium lacustre is not similar to any specimen I have seen being too inflated. The Recent and detailed Late Pleistocene-Holocene distributions are given together with a map. Many species are now very restricted and the author points out that almost all are under threat from pollution. Some synonymy is given and for some species extensive bionomic details under the remarks. Original places of publication are not given for cither the correct names or the synonyms and for these Pilsbry and Bequaert is still required. Much space is saved by these omissions and in any case those who need such details know where to find them. The type localities are, however, given for each species.

Part two details the distribution of freshwater molluscs over the whole of Africa succinctly, region by region, in a way which complements rather than replaces Brown's account. It confirms only what is already known save that the Palaearctic-Ethiopian demarcation line is defined in much more detail. Parts three and four are I think the most valuable and deal with Cretaceous and Tertiary history, including evidence available from beyond the strict region concerned, and with the Quaternary fauna of northern Africa respectively. They give a much-needed summary of recent work. I was surprised at the amount of material now available. In the first half of the Cretaceous the fauna was rich, particularly in bivalves, and has declined since; in particular that universal extinction which struck at the end of the Cretaceous. From the Palaeocene up to the early Miocene Ampullariids flourished in extensive swamps, a conclusion I also reached when dealing with Kenya deposits. The great and rather puzzling difference between the fauna of much of northern Africa, derived almost entirely from Europe and Asia when the Atlas chain was geologically new, and the Afrotropical fauna is partly explained by a shallow sea existing before the Mid-Miocene; the Afrotropical species were later unable to oust species which had become well-adapted to hot often brackish conditions. The development of deep lakes had a great influence on mollusc evolution. The unique fauna of Lake Tanganyika may not have been the result of gradual evolution over a long period as generally believed but due to bursts of speciation followed by periods of stability. This follows studies of the Pliocene Lake Kaiso and Lake Turkana (Williamson's punctuated equilibrium model) (Figs. 141 and 142 show this pictorially). During the Pliocene the radiation of the Pulmonate species, now so common, started. Except for further extinctions there has been little change since. Part 4, the most interesting of all, deals with times slowly more and more dominated by man and will thus be that most important to anthropologists and archaeologists. In northern Africa it is the history of unstable environments with repeated colonizations and extinctions mirroring numerous climatic changes. This results in little evolutionary change and the most recent speciation is early Pliocene or earlier. Interesting is the fact that the present Sahara had its initiation during the late Pliocene. A short essay on dispersal modes contains the novel suggestion that Darwin's famous record of an adult Anodonta attached to a duck's foot might be the result of a practical joke -but of course quite without evidence.

A list of all the localities mentioned is very useful and correlated with the map.fig. 144 (although this is not mentioned in either the map-caption or the list-heading although they are 12 pages apart). The 9 pages of bibliography are exhaustive and extremely valuable although the absence of Hamilton's Environmental History of East Africa (1982) is surprising. The two indexes seem complete.

There are rather too frequent misprints, many of the same kind involving double letters e.g. p. 39 'Connoly', p. 55 'neat', p. 95 'Ampulariidae', p. 97 'Gabiella', p. 104 'Quadrulla', p. 116 'Peudodiplodon', p. 136, 'Pre- Cambrium' and some oddities e.g. the hybrid English-French p. 53 and 105 'conchyologically', p. 112 'conchyological' also p. 2 'epigons' (surely used in the wrong sense). Still let us be thankful the text is in English! The use of italic and Roman script is somewhat erratic e.g. in the list of contents where some authorities are also missing - this right at the beginning of a book gives a bad impression and should have been picked up by readers. The abbreviation a.o. which appears in various places seems to mean e.g. but remains a mystery to me. One reference on p. 117 puzzles me; the author quotes Oswald in Verdcourt 1963 although Oswald was long dead when I wrote on the Miocene Mollusca of Rusinga etc. and he also makes reference to Cleopatra amoena=ferruginea but these are not mentioned in my paper. The reference is really to R. Bullen Newton's paper describing Oswald's material and the species concerned was claimed to be C. exarata.

Reviewers have mostly ceased their once perennial complaints about the price of books but 164 pages and no plates, not even black and white, for approximately £35 is I think very steep. What is more it just encourages illegal copying with the superb modern copiers now available for a fraction of the price. I know all the publisher's explanations of these prices by heart but am still not convinced that a wider sale which includes ordinary folk would not net more profit. Those who need this book will have to use institutional copies.

This aesthetically dull group does not attract many collectors but the extreme value of molluscs as climatic indicators means this book will be required reading for all interested in the climatic history of the Sahara from the Cretaceous right up to modern times and other parts of Palaearctic Africa.