376 CRETACEOIJS PELECYPODA 



ah umhone idriusque valvulce oblique ad marginem ventralem decurrente, antice et 

 postice sulculis marginata. 



Lengtli of shell : height ... ... ... ... I'SO 



„ „ : thickness ... ... ... ... 1"33 



This is one of the very few species which by its short tumid form, concentric 

 striae of growth, and the broad incurved beaks, indicate the occurrence of the sub- 

 genus Botula in cretaceous deposits. The species is particularly characterized by 

 the sub-median depression fvide pi. xxxviii, fig. 13), which extends from the beak 

 of each valve to about the middle of the ventral portion. 



Locality. — South-east of Arrialoor, in a conglomeratic whitish sandstone ; only 

 the figured specimen has been found. 



Formation, — -Arrialoor group. 



2. LiTHODOMTJS cunTA, Stoliczka, PL XXIII, Eig. 17. 



Lith. testa ovato-cylindracea, antice ac postice sub-t7'uncata, umhonibus anticis^ 

 parvulis^ superficie concentrice striata. 



Length of shell : height... ... ... ... ... 1*8 



„ ,, : thickness ... ... ... ... 1*82 



The single specimen known is not in a very good state of preservation, but 

 the short, almost quite cylindrical, form is so characteristic that the species can 

 be readily distinguished by it. Both the ends are sub-truncate, the anterior slightly 

 convex, the posterior somewhat obliquely obtuse, which form distinguishes the 

 Indian species from iz77z. a^^Z^(^7^a, d'Orb. Portions of the surface of shell only 

 indicate the presence of striae of growth. 



Locality, — Odium ; found boring in yellowish earthy limestone. 



Formation, — Ootatoor group. 



3. LiTHODOMUS SUB-CYLINDRICA, StoUczlm, PL XXIII, Eigs. 18-19. 



Lith, testa pistilliformi^ cylindracea^ postice gradatim compressiuscula^ ad 

 utramque terminationem sub-rotundata^ umbonibus sub-tei^minalibus, anticis, parms^ 

 incurvis ; superficie striis acutis^ sulculis nonnullis interpositis, concentricis, tecta. 



Length of shell : height ... ... ... 2-67 



: thickness ... ... ... 2-67 - 2-68 



The anterior part of the shell is almost perfectly cylindrical, towards the 

 posterior end the form becomes laterally compressed, and so far agrees very well 

 with that of Lith. rugosa, d'Orb., but the Indian species wants the peculiar trans- 

 verse striation on the ventral side which distinguishes the European fossil. 



It could be supposed from the imperfect figure given in the Trans. Geol. Soc, 

 Lond., vii, pi. xvi, fig. 7, that Litli. sub-cylindrica is the same sheilas Eorbes' 

 Mytilus cypris, this species having been by European authors also referred to 

 Lithodomus ; such is, however, not the case, as may be seen by a comparison of the 



