Fresh-water Peculiar to Total sp. Land sp. sp. Peculiar group Mauritius 113 104 9 78 102 (90 p.c.) Bourbon 45 40 5 19 38 (84 p.c.) Rodriguez 23 19 4 15 21 (95 p.c.) Seychelles 34 27 7 24 30 (90 p.c.) The Mollusca of the group exhibit three distinct elements, the Indigenous, the Madagascan, and the Indian and Australasian. The genus _Pachystyla_ (Naninidae) is quite peculiar, forming the main portion of the land snails proper. It attains its maximum in Mauritius (17 sp.), with 5 sp. in Bourbon and one sub-fossil sp. in Rodriguez, while in the Seychelles it is absent. But the principal feature of the Mascarene group is the extraordinary development of the carnivorous genus _Gibbus_, which has 27 sp. in Mauritius, 8 in Bourbon, 4 in Rodriguez; in the Seychelles, it is replaced by _Edentulina_ and _Streptostele_. The principal link with Madagascar is found in a part of the operculate land fauna. _Cyclostoma_ is present (with _Otopoma_) in several fine living forms, and the number of sub-fossil species is a clear indication that this group was, not long ago, much more abundant, for of the 16 _Cyclostoma_ known from Mauritius 10 are sub-fossil. The operculates form a decided feature of the land fauna; thus in Mauritius there are 32 species, or more than 28 per cent of the whole. [Illustration: FIG. 225.--Characteristic Mauritian land shells: =A=, _Gibbus palanga_ Fér.; =A´=, young of same; =B=, _Gibbus lyonetianus_ Pall.] Indian and Australasian affinities are unmistakably present. Thus _Omphalotropis_, a genus characteristic of _small_ islands, is profusely represented, but it does not occur in Madagascar or Africa. Two _Helicina_ (Mauritius and Seychelles) and a single _Leptopoma_ (possibly a _Leptopomoides_) are also of eastern relationship. _Cyclotopsis_, _Cyathopoma_, and _Geostilbia_ are markedly Indian genera. _Microcystis_, _Patula_, and _Tornatellina_ are Polynesian. _Hyalimax_--and this is a very striking fact--occurs nowhere else but in the Andamans and Nicobars, and on the Aracan coast. The nearest relation to the Seychelles _Mariaella_ appears to be the Cingalese _Tennentia_. Not a single representative of these eleven genera has been found even in Madagascar.