The Strophocheilidae contain some of the largest living terrestrial snails, they are amongst the more conspicuous members of the South American fauna. Being at the same time peculiar to the New World, they are one of the distinctive elements of the Neotropical Region. To the zoogeographer they are of more than usual interest as representing a S„ American branch of the Acavid stock, an ancient, primitive group of pulmonate land snails with a disconnected circumpolar distribution in the Southern Hemisphere. Most authors speculate that the ancestors of the recent superfamily Acavacea originated at some remote geological period (probably before the Mesozoic) on a single fairly continuous Austral continent extending perhaps at one time from the S. Pole to near the Equator. When this hypothetical 'Gondwana Continent' broke up, supposedly from the middle of the Mesozoic onward, it is claimed that the descendents of the primitive Acavacea became isolated in four widely disconnected areas, where further evolution event¬ually produced a number of distinct Recent groups, now ranked either as families or subfamilies. These areas are Australia, Madagascar and Ceylon, South Africa and South America.
In South America the superfamily seems to have survived well, as it now covers a very wide area and comprises more species than elsewhere, the majority of them being bulimoid (Strophocheilidae), with a few helicoid forms (Macrocyclidae) restricted to Chile. Some authorities believe that the Strophocheilidae are amongst the most primitive of the Recent Acavacea, which might indicate that South America was furthest from the primitive centre of evolution of the superfamily. Moreover, the Strophocheilidae probably arose from the same ancestoral stock as the Bulimulidae, a non- acavid family of land snails now dominant in the New World tropics.
The Strophocheilidae are divided into two Genera, Strophocheilus and Gongostomus. In Strophocheilus five subgenera are recognised, Strophocheilus, Speironepion, Megalobulimus, Austroborus and Chiliborus, and in Gongostonru,: two, Gongostomus and Anthinus.
The family is indigenous in S. America north of 40° Lat. S., including Trinidad. The occurrence of S. (M) oblongus (Mull.) in some of the Antilles proper is due to introduction by man. None have been found north of the Isthmus of Panama. There appear to be four main centres of density of species. The most important of these is in the eastern half of Brazil, from Maranhao to Rio Grande de Sul, the home of all the 4 species of Gongostomus, 2 species of Speironepion and 7 species of Strophocheilus s.s., as well as 10 species of Megalobulimus. A second centre is in the Andean area, from Bolivia to Colombia, which harbors 8 species of Megalobulimus. The subgenera Austroborus (3 species) is peculiar to Uruguay and Northern Argentina, while Chiliborus (4 species) is restricted to Central Chile. Only one species, S. oblongus is more generally distributed and has produced some peculiar races in Southern Brazil and the Uruguay-Argentina area.
The very large species of the subgenera Megalobulimus are exceeded in size only by certain African Achatinidae and are amongst the largest known living terrestrial snails, S. (m) propelairianus (Nyst) from Ecuador attaining a length of 163 mm. The families Strophocheilidae and Aohatinidae seem to replace each other on their respective continents, where they occupy to some extent the same ecological niche;, The South African Metachatina and the Central African Burtoa particularly simulate certain species of Megalobulimus, the shells of the two families having become superficially similar through convergence.
All the Strophcheilidae are terrestrial, most of them prefer well- sheltered, damp, deeply shaded places, densely covered with vegetation, such aa ravines in virgin forest. They appear to be nocturnal, hiding under humus or in loose soil by day. At times of drought they bury deep down in the ground or crawl into crevices of rocks or in caves, where they aestivate, after closing the aperture with an epiphragram. As a result of the destruction of the forests in certain parts of Brazil, some of the species have become very scarce or possibly even extinct. The species of Chiliborus and Austroborus favour a more xerophytic environment and hide beneath rocks or in loose sand.
Several of the larger species were formerly eaten by the Honative Indians and S. ovatus was still offered for sale in the markets of Rio de Janeiro as late as I867. This custom seems, however, to have been discontinued.
The eggs of the big species of Megalohulimus are very striking objects on account of their size, that of S. (M) propelairianus being as large as that of the common pigeon. In Barbados, the white of the egg of S. (M) oblongus has been used as a glue to mend china and glass and is claimed to be superior for this end to any manufactured product.
T. Pain