HIPPURITES. 171 



patelliform univalves ; to some of which, particularly Pileopsis, 

 they bear a very strong resemblance. The species of Hipponyx 

 are numerous, and till lately only knovni in a fossil state. The 

 recent species belong to tropical climates : the fossil species are 

 found in the tertiary beds. The monograph in the Thesaurus 

 Conchyliorum contains five species. H, cornocopia. PI. xi. 

 figs. 199, 200. 



HIPPOPODIUM. Conybeare. J. Sowerby, 1819. Fam. 

 Cardiacea, Lam. — Bescr. Equivalve, obliquely transverse, heavy, 

 deep, inequilateral, umbones incurved ; ventral margin sinuated, 

 so as to give a bilobed appearance to the shell ; hiage in- 

 crassated, with one rugged obHque tooth. — Obs. These fossila 

 are found in the upper beds of Lias. H. Ponderosum. PI. vii. 

 fig. 129. 



HIPPOPUS. Lam, ('Ittttoc, hippus ; vovg, pous, foot.) Fam. 

 Tridacnacea, Lam. — Bescr. Equivalve, inequilateral, regular, 

 subquadrate ; lunule closed, flat, with crenulated edges ; ventral 

 margin deeply undulated ; external surface fluted, with radiatiag 

 ribs, which are transversely fringed with rows of tubular spines ; 

 hinge margin thick, with two long, compressed posterior lateral 

 teeth in one valve, three in the other ; ligament marginal, exter- 

 nal. — Ohs. The shell thus described is rightly separated from 

 Tridacna, on account of the anterior dorsal margins being closed ; 

 whereas in Tridacna there is a wide hiatus. Only one species of 

 this genus is known, which receives its name from its resem- 

 blance in form to a horse's foot, when held with the flat anterior 

 dorsal margin downwards. Few shells are found to concentrate 

 so many beauties as the Hippopus Maculatus, commonly called 

 the Bear's-paw-clam ; the delicate whiteness of the interior, the 

 undulating edge, the radiated fluted columns, adorned at inter- 

 vals by crisped fringes, and the richness of the variegated colour- 

 ing, are such as to secure the admiration of the most superficial 

 observer. Erom the Indian Archipelago. H. Maculatus. PL ix. 

 fig. 156. 



HIPPUEITES. Montf. Fam. Orthocerata, Lam. Eudistes, Bl. 



