PKOCKEDINGS OF THE MALACOLOGICAL SOCIKTY. 



tortuous. They may extend from the central ridge to the margin, but, as 

 a rule, they are short, and many of them reach neither the central ridge 

 nor the outer edge. The upper extremity of the central ridge is pierced 

 with a narrow slit a little more than a millimetre in length. _ Its position 

 is relatively the same as the slit in the epijAragm of Achatina as figured 

 in the "Proceedings" of the Society, vol. iii, p. 309. It doubtless 

 corresponds to a slit in the mantle leading to the respiratory orifice. The 

 outer or curved margin exhibits from end to end a series of minute 

 perforations. They look as if they have been pricked through from the 

 inner surface, each being upon a little prominence. On the under surface 

 each perforation is more or less surrounded by a raised short ridge-like 

 loop, the ends of which are open on the inner side. The outer surface is 

 rather uneven, but, with the exception of the outer perforated edge, is 

 generally rather smooth. 



1. 2. 



Fig. 1. — Epiphragm of Thaumastus Smigom. 

 Fig. 2. ,, ,, bitceuiatus. 



The epiphragm of Thaumastus hit<xniatus of Nyst is much more simple 

 in character, having no series of perforations along the outer margin, and 

 very feeble indications of radiating ridges beneath. There is a broken-up 

 thin central keel, with a perforation in the same position as in T. Sangoa;. 

 It is, however, not such a narrow slit as in that species. The outer surface 

 is fairly smooth, although uneven. 



It is interesting to have for examination the epiphragms of two species 

 from the same locality (Chanchamayo, Peru) and belonging to the same 

 genus, for their differences tend to show that in these structures we may 

 find additional si^ecific characters. Both these epiphragms are white, as is 

 frequently the case in other species. This colour, however, is not universal, 

 for in Liguus virginicus and Oi-thalicns zebra it is said to be green, and in 

 the latter species, although thick and solid, it is described as glutinous 

 rather than calcareous (Crosse & Fischer, " Mission Scientifique au 

 Mexique," Mollusques, vol. i, p. 447, pi. xviii, figs, 8, 8a). 



E. A. Smith. 



