MOLLUSCAN GENUS COCHLITOMA. 



251 



former. The ureter opens by a wide and non-plicate aperture 

 anteriorly to the anus. In front of the ureter lies a small lobe. 

 A certain amount of distortion made it impossible to compare z 

 and z.^ in this respect. 



Internal Anatomy. 

 (1) Alimentary Canal. 



The jaw was examined only in the case of z.,, that of z being 

 previously damaged. 



Viewed anteriorly the jaxv is mai^kedly lunate and its antero- 

 dorsal surface is very wide. The interior surface is covered by 

 a fairly dense cuticle which is continued backwards and round 

 the sides and bottom of the mouth. It is more dense dorsally 

 and is continued posteriorly for about 5-6 mm., but is not con- 

 tinued on to the antero-dorsal plate. There is on this cuticle 

 a faint but definite striation. The weak ribbing seen in var. 

 fulgurata is represented only by a few irregular faint dark lines 

 which can be seen luider a high power. 



Text-fisfure 1. 



CocMifoma zebra var. ohesa. 



Radula; median and admedian teetli. Fosition of degenerate entocone sliown 



\>y dotted line. 



The radula. (Text-fig. 1.) 



Formula:— z^ 80. 1. 80. xl33. 



z, 69. 1. 69. xl33. 



Another example from the") g- ■. g« x 124 -hi 



Gwatkin collection J ' * ' / ~~ ' 



These figures represent maxima. 



For the purpose of this study only the median, the first two 

 admedian and the adlateral teeth were compared. 



Proc. Zool. Soc— 1 921 , No. XVIII. 1 8 



