438 EXPLANATION OF PLATES. 



FlGUKE. PAGE. 



8,9. Requienia Lonsdalii, J, Sowb. Neocomian ; Eur., 200 

 10,11. Requienia ammoma, Goldf. Cret. ; Europe,. . 200 



12. Requienia. Internal cast, c, cast of dental pit ; f', 



furrow of spiral ridge, 200 



13. Caprina adversa, d'Orb. Cret. ; France, . . . 200 



14. 1ft. Caprotina striata, d'Orb. U. Greensand ; France, . 201 

 16, 17. Chamostrcea albida. Lam. New South Wales, . 202 



18. Hippurites cornu-vaccinum, Bronn. Salzburg. Lon- 



gitudinal section taken through the teeth (t, t')^ and 

 apophyses (a, a'). cZ, outer, r. inner shell-layer; Z, 

 dental plate of lower valve ; u, umbonal cavity of 

 upper valve ; t, intestinal channel. Original in 

 Brit. Mus., 204 



19. Ibid. Longitudinal section ; upper half, one-half natural 



size. II, umbonal cavity of left valve ; r, of right 

 valve; /, ^', teeth ; a, muscular apoph3^sis ; t?, outer 

 shell-layer. The figure is taken in the line d, &, fig. 

 24, PI. 118, cutting only the base of the posterior 

 tooth, t, 204 



20. 21. Dicerocardium Jani, Stoppani. Triassic ; N.Italy, 208 



Plate 118. 



18. Caprinella Aguilloni (left valve), a, a', position of 



adductors ; Z, ligament ; u, umbonal cavity ; t, tooth 



of fixed valve broken off and remaining in its socket, 201 



19. Caprina adversa, d'Orb. Cret. ; Europe, . . . 200 



21. Caprotina quadripartita, d'Orb. Internal cast. z(, left 



umbo ; r, right umbo ; Z, ligamental inflection ; e, 

 cartilage ; t, t', dental sockets ; a', position of 

 adductor; at e, a portion of the third lobe is broken 

 away, 201 



22. 23. Caprinella triangularis, Desm. U. Greensand, 



Rochelle, France. Fig. 23 is a mould of the body 

 chamber ; w, umbo of right valve ; .s, of left valve ; 

 Z, dental groove ; a, surface from which the posterior 



lobe has been detached, 201 



24. Hippurites cornu-vaccinura, Bronn. Salzburg. Trans- 

 verse section. Z, m, n, duplicatures ; r, umbonal 

 cavity of right valve ; e, c', cartilage-pits ; Z, teeth ; 

 a, a', muscular apophyses ; d, outer shell-layer. Fig. 

 24 is from a larger specimen, at about the level d b, 

 of fig. 19, PL 117, cutting the point of the posterior 

 apophysis (a'), and showing the peculiar shell -texture 

 deposited by the anterior adductor (a), . . . 204 



