MANUAL OF THE MOLLUSCA. 



I, 



Fig. 198. Longitudinal section; upper half, |. Fig. 199. Transverse section, -. 



Hippurites cornu-vaccinum, JBronn. Salzburg. 



/, m, n, duplicatures ; u, umbonal cavity of left valve; r, of right valve; c, c', car 

 tilage-pits; t, t', teeth; a,V, muscular apophyses; d, outer shell-layer, Fig. 198 i 

 taken in the line d, b, of fig. 199, cutting only the base of the posterior tooth (f ) 

 Fig. 199, is from a larger specimen, at about the level d, b of fig. 198, cutting the poin 

 of the posterior apophysis (a'), and shewing the peculiar shell-texture deposited by 

 the anterior adductor (a). 



of the teeth and adductors further from the hinge-margin, to a position in 

 which the muscles must have been unusually long, unless supported in the 

 manner described. Supposing the animal to have had a small foot,* like 



Fig. 200. Hippurites cornu-vaccinum. Fig. 201. Radiolites cylindraceus, %. 



Longitudinal sections taken through the teeth (t, f) and apophyses (a, a'). 



d, outer, r, inner shell-layer ; I, dental plate of lower valve ; u, umbonal cavity of 



upper valves ; i, intestinal channel. Originals in Brit. M. 



* This is extremely doubtful ; since p. 253 was printed, we have examined an 

 authentic specimen of Aetheria, and find that Rang and Cailliaud's account is incor- 

 rect : it has no foot. 



