202 lAND AND FRESHWATER 



the passage through the folds is generallj' found to be filled up with 

 mucous secietiou, but the body itself mostly retracts one-half of a 

 whorl further inwards. During hybernation the aperture is besides 

 closed with the usual lamina as in other Helicidse. I have exa- 

 mined the animals of Ph achatina, cyclaspis, pinacis, and macrom- 

 johalus. They are all very similar in external shape and organiza- 

 tion. I will for the present note only the two first-named species, 

 which occur near Moulmein." 



After describing the external appearance of the animal in detail 

 he continues, on p. 219 : — 



" On the whole, the form of the body very closely resembles that 

 of a Clausilia, and a comparison of the internal organization of the 

 two genera also indicates their close relation." 



Then follows the description of the internal organs, which I shall 

 not give here. On p. 220 is this interesting remark : — 



" All the species which I have examined are ovo-viviparous, as 

 already noticed by Benson in F, achatina. One specimen of 

 P. cyclaspis had three well-developed embryos, each consisting of 

 three convolutions, regularly coiled in and enclosed in a thin soft 

 sac of calcareous granules, loosely jointed together. A specimen 

 of P. pinacis had the whole uterus tilled with 13 eggs, in different 

 stages of development. The first were perfectly developed, com- 

 posed of 2j whorls, distinctly discernible. The youngest only con- 

 sisted of a yolk- mass, darker internally than externally and folded 

 on itself hemispherically like an enrolled Oniscus. The jaw is very 

 thin, horny, semielliptical, with a small anterior median projection ; 

 it is marked transversely with a great number of more or less 

 distant grooves which divaricate in the centre. The surface 

 often besides shows in a transparent light a very fine concentric 

 striation, either on the entire jaw or only on its median portion." 



We then have a full description of the radula, still on p. 220 : — 



" On comparing the jaw of Plectopylis with that of Clausilia it 

 will be seen that both are similar in structure, but the shape is 

 different and the transverse sulcations are only indicated in the 

 latter genus. Much greater is the similarity of the Plectopylis jaw 

 with that of Cyllndrdla as published by Crosse & Fischer in Journ. 

 de Conch, vol. x. 1870, p. 5 &c. pis. iii. & iv., with the exception 

 that the median projection is wanting in the Cylindrella jaw. 



" The arrangement of the teeth of P. achatina and cyclasp)is also 

 agrees with that of Cylindrella in the ver)' small size of the centre 

 tooth, but this is not a constant character. In P. pinacis the 

 centre tooth is larger and more of a shape similar to that of the 

 lateral teeth, which, however, in all the species retain distinctly 

 the helicoid character." 



Considering the uncertain variable utility of the generic divisions 

 of the Terrestrial Mollusca and at the same time how far back in 

 time some of these genera existed, I cannot imagine there is any very 

 close relationship between Corilla, Plectopylis, and Clausilia, or 

 that there is much that can be termed analogous in the clausilium 

 of the latter witli the internal pyloric plication of the two former, 



