252 



Records of the Indian Mttseum. 



[Vol. XXII, 



It has not been necessary to say much about the edge of the 

 mantle between the processes, the external structure of which of- 

 fers no particular feature of interest at any time of life in most 

 species. The difference between its conformation in Vivipara and 

 Taia on the one hand and Lccythoconcha and Margarya on the 

 other, already noted in the young (p. 249), is accentuated with the 

 growth of the individual. It is, however, somewhat exaggerated 

 in highty contracted or shrunken specimens. Another important 

 generic difference, not following the same lines of division, may 

 now be noted. It has a much more direct bearing on the special 

 object of this section of our paper, as it is evidently correlated with 

 the glj'ptic ornamentation of the shell. In Vivipara and Lccytho- 

 concha the edge when fulh' expanded is straight, or rather curved 

 in a wide arc outwards. It is, indeed, capable of considerable 



c.e. 



n^-9^ 



^'^' 





"f#o 



Fig. I4. — Horizontal transverse section tbrougli part of the edge of the 

 mantle at the base of a primary marginal process of an adult Vivipara nxvtropis 

 (Benson), highly magnified and slightly diagrammatic. 



c, calcareous concretions; c.i?.. ciliated epithelium; m.g., marginal groove of 

 primary marginal process; /;., pigment granules; p.g., periostracal glands; s.g., 

 calciferous glands. 



change of shape and may become distinctl5' sinuate ; but the irre- 

 gularities of outline are mere irregularities without definite posi- 

 tion or apparent function. This is also so in L. lecythis. It is 

 unfortunate that I have not had an opportunity of examining 

 either Taia or Margarya in a living condition in this connection, 

 and in contracted specimens of these genera preserved in alcohol I 

 can find no peculiarity of the edge of the mantle. In 3'oung exam- 

 ples of Taia intha, however, which were paralysed with menthol 

 and fixed in 5% formalin without being fulh' contracted, a broad 

 lobular projection can be detected at the base of the terminal 

 scale-like projection on the peripheral ridge of the shell, proceeding 

 for a short distance into the anterior cavity of the projection. 



Epithelium. — The epithelium of the extreme edge of the 

 mantle is, as already stated, provided with long and powerful 



