CONCH1FERA. 



289 



the spire downwards. (Saemann). The lower valve of C. Coquandiana is 

 sub-spiral. 



Fossil, 5 sp. U. Green-sand and L. Chalk. Bohemia, France, Texas. 



Fig. 212. Internal mould of Caprotina quadripartita, D'Orb. 

 , left umbo; r, right umbo; I, ligamental inflection; c, cartilage; t , V, dental 

 sockets ; a, a', position of adductors ; at e, a portion of the third lobe is broken away.* 

 From a specimen collected by Mr. Pratt. 



CAPROTINA, D'Orbigny. 



Type, C. semistriata, PI. XIX. fig. 13, 14. Le Mans, Sarthe. 



Shell composed of two distinct layers ; valves alike in structure, dis- 

 similar 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 ligamental inflection, posterior 

 adductor supported by a plate : free valve flat or convex, with a marginal 

 umbo; teeth 2, very prominent, supported by ridges (apophyses) of the 

 adductor muscles (a, a?}, the anterior tooth connected with a third plate (n), 

 which divides the umbonal cavity. 



The smaller Caprotinte occur in groups, attached to oyster-shells ; their 

 muscular ridges are much less developed than in the large species (fig. 212), 

 6'. costata is like a little Radiolite. 



Fossil, 4 sp. U. Green-sand, France. (The rest are Chamas, &c.) 



FAMILY IX. 



Shell regular, equivalve, truncated in front ; ligament external ; valves 

 strongly ribbed, margins toothed ; muscular impressions blended, sub-Qentral, 

 obscure. 



Animal attached by a byssus, or free; mantle-lobe extensively united ; 



* The first and fourth lobes, those on each side of the ligamental inflection, appear 

 to be the two divisions of a great internal cartilage, like that of the Radiolite. (Fig. 

 205, 206, c, c.) 



