CONCHIFERA. 451 
Fossil, 10 species. Upper Greensand and Lower Chalk, 
Bohemia, France, Texas. 
nae, 
WUM Es, 
\\\i "aN 
Fig, 251. Internal mould of Capretina quadripartita, D’OrD., $. 
u, left umbo; 7, right umbo; J, ligamental inflection; ¢, cartilage ; t,t’, dental sockets 
a, a', position of adductors; at e, a portion of tra thicd lobe is broken away.* Froma 
specimen collected by Mr. Pratt. 
CaPRoTINA, D’Orbigny. 
Type, C. semistriata, Pl. XIX., Figs. 13 and 14. Le Mans, 
Sarthe. 
Shell composed of two distinct layers; valves alike in struc- 
ture, dissimilar in sculpturing; ligamental groove slight ; 
cartilage internal ; right valve fixed, striated, or ribbed, with one 
narrow tooth between two deep pits, cartilage pits several on 
each side of the igamental inflection, posterior adductor sup- 
ported by a plate: free valve flat or convex, with a marginal 
umbo; teeth 2, very prominent, supported by ridges (apophyses) 
of the adductor muscles (aa’), the anterior tooth connected with 
a third plate (7), which divides the umbonal cavity. 
The smaller Caprotine occur in groups, attached to oyater- 
shells; their muscular ridges are much less developed than in 
the large species (ig. 251). C. costata is like a little Radiolite. 
Fossil, 10 species. Upper Greensand, France. (The rest are 
Chamas, «&c.) 
FamIty 1X.—TRIDAONIDE. 
Shell regular, equiyalve, truncated in front; lgament 
external; valves strongly ribbed, margins toothed ; muscular 
umpressions blended, sub-central. obscure. 
* The first and fourth lobes, those on each side of the ligamental inflection, appear 
to be the two divisions of a greet internal cartilage, iike that of the Radiolite. (Figs 
244, 245, c, c.) 
