438 EXPLANATION OF PLATES. 
FiGURE. PAGE, 
Requienia Lonsdalii, J. Sowb. Neocomian; Eur., 200 
10, 11. Requienia ammonia, Goldf. Cret.; Europe, . . 200 
12. Requienia. Internal cast. c, cast of dental pit; 
furrow of spiral ridge, : : : . 200 
13. Caprina adversa, d’ Orb. Oret. : France, : : . 200 
14, 15. Caprotina stri iata, d’Orb. U. Greensand ; France, . 201 
16, 17. Chamostrza albida, Lam. New South Wales, . 202 
18. Hippurites cornu-vaccinum, Bronn. Salzburg. Lon- 
gitudinal section taken through the teeth (¢, ¢’), and 
apophyses (a,a’). d, outer, r, inner shell-layer; J, 
dental plate of lower valve; u, umbonal cavity of 
upper valve; 7, intestinal channel. Original in 
Brit. Mus., . ; . 204 
i.) Tbid: Longitudinal section ; upper ‘half, one- half natural 
Sizeve 1, -umbonal cay ity of left valve ; r,of right 
valve; ¢, ¢’, teeth; a, muscular apophysis; d, outer 
shell-layer. The figure is taken in the line d, }, fig. 
24, Pl. 118, cutting only the base of the posterior 
tooth, ts i ; : : d é . 204 
20, 21. Dicerocardium Jani, "“Stoppani. Triassic ; N. Italy, 208 
PLATE 118. 
18. Caprinella Aguilloni (left valve). a, a’, position of 
adductors; J, ligament; uw, umbonal cavity; ¢, 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. Internalcast. wu, left 
umbo; 7, right umbo; /, ligamental inflection; ec, 
cartilage; ¢, ¢’, 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; u, umbo of. right valve; s, of left valve; 
t, dental groove; a, surface from which the posterior 
lobe has been detached, . 5 : : . 201 
24. Hippurites cornu-vaccinum, Bronn. Salzburg. Trans- 
verse section. J, m, n, duplicatures; r, umbonal 
cavity of right valve; c,c’, cartilage-pits; ¢, 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) sus : . 204 
