CONCHTFEEA. 



447 



the deep and rago«e cartilage pits : loiuer valve witli a thict outer 

 layoi, offcon foliaceous ; its cavity deep and straight, ^vith two 



Fig. 241. Interior of lower valve. Fig. 2-12. Interior of upper valve. 



Badiolites mammillaris, Math. |. L. Chalk. S. Mamest, Dordogne. 



I, ligamental inflection; m, pallial line ; c, c, cartilage pits ; a, a, adductor impressions 



and processes ; t, teeth and'dental sockets. 



dental sockets and lateral muscular impressions; upper valvt 

 fiat or conical, -^th a central umbo ; outer layer thin, radiated ; 



Fig. 243. Side views of the upper valve of E. mammiUaria ; /, ligamental inflection ! 

 t, teeth ; a, a', muscular processes. 



umbonal cavity inclined towards the ligament ; teeth angular, 

 striated, supporting.curved and sub-equal muscular processes. 



The upper valve of R. fieuriausus has an oblique umbo, ^nth 

 a distinct ligamental groove. The* foliations of the lower valve 

 are frequently undulated ; they are sometimes as thin as paper, 

 and several inches wide. 



The umbonal cavity of the lower valve is partitioned off by 

 very delicate funnel-shaped laminae. Specimens frequently 

 occur in which the outer shell layer is preserved, whilst the 

 inner is wanting, and the mould (" birostrites") remains loose 

 in the centre. The interior of the outer shell layer is deeply 



