UNDESCR1BED FOEM OF GASTEROPOD MOLLUSK. 423 



opens by a wide orifice under the overhanging lateral angles 

 of this mantle, which are slightly curled up or elevated. The 

 cavities nearly meet from the opposite sides, and appear to be 

 the real terminations in front of the lateral grooves. The 

 bronchiae consist of from twelve to fifteen lamina?, closely set 

 together, extending from before backwards, longer internally 

 in the cavity than externally, where they are small, short, and 

 indistinct. The larger laminae at the inner part of the series 

 are attached to the vault of the cavity ; the shorter, less dis- 

 tinct plates depend from the under surface of the projecting 

 margin of the mantle. The laminae are of a light brownish- 

 yellow colour, and appear each to consist of a double mem- 

 brane with a quarter lens ; and under a favourable light, a 

 number of faint opaque lines, each of which presents a few 

 dots, apparently orifices, may be observed to be arranged on 

 the under surface of the anterior half of the projecting margin 

 of the mantle. Each line runs obliquely from behind forwards 

 and inwards. 



The common genital vestibule is situated in the right 

 lateral groove, immediately behind and below the bronchial 

 chamber. It is circular. From its anterior compartment an 

 elongated male organ projects. Its posterior compartment 

 presents the opening of the female organs. 



The anus is situated on the apex of a cylindrical papilla, 

 at the middle of the right lateral groove. 



This animal is evidently an infero-branchiate mollusk. 

 In the position of the anus, and in its characters generally, 

 it closely resembles Diphyllidia, but differs from that genus 

 in the arrangement of the branchiae, which, instead of con- 

 sisting of a series of oblique laminae arranged along the 

 two posterior thirds of each lateral groove, are in the form 

 of transverse series of longitudinal Laminae depending from 

 the roofs of tin-, two Lateral cavities. So very marked was 

 the apparent difference between my specimen and the 



