PLATE XXL 



Figs. 1 — 3. Radiolites mt.'tabii.is, Slol., p. 241 ; 1, umbonal view of a specimen on which the shell 

 of the lower valve has been removed; ck is the basal portion of the lower valve, with 

 the beginning of the chambered part ; t and P are the serrated hinge-teeth of the 

 upper valve ; in n arc the muscular scars, the upper valve is perfect ; 2, is the front- 

 \aew of a nearly perfect specimen, showing the large umbonal area with a ridge 

 along the middle ; h indicates the region of the hinge; /J the place of attachment; 

 3, is a short and broad specimen from which the shell of the iipper valve has been 

 removed ; h indicates the hinge region ; m, are the muscular scars seated on a horse- 

 shoe-shaped process, posteriorly separated by an excavation ; c is the cartilage 

 region ; Comarapolliam, Arrialoor group. 



Fig. ... 4. SpH.s;iitrLiTES indica, StoL, p. 242 ; 4, side-view of an imperfect lower valve ; a 

 narrow longitudinal portion of the shell is broken away, allowing the internal hinge 

 rib to become visible ; 4 a is the top-view of the same valve in a somewhat oblique 

 position, vrith the external foliated margin partially preserved; h indicates the 

 region of the hinge ; Odium, Ootatoor group. 



