264, MAZATLAN UNIVALVES 
adopted from their great convenience. Of Calyptrea proper, 
which is the best marked in its characters and is well repre- 
sented both in individuals and species in the Caribbean and 
equatorial West American Seas, only a single individual was 
found in the entire Mazatlan collection. None of the species 
were found with a solid sheily attachment, though a thin 
deposit may sometimes perhaps be traced. In general a cavity 
is excavated on the backs of other shells. 
Famity CALYPTRAIDA. 
Genus TROCHITA, Schum. 
Schum. Ess. no. 11, 1815.—Gray, Proce. Zool. Soc. 1847, p. 188, 
no. 272.—Phil. Handb. Conch. p. 187.—H. & A. Ad. Gen. i. 
367. 
Trochus, pars, Laim.—Calyptrea, pars, Desh. Sigapatella, Less, 
1829, Voy. Coqg.—Trochatella, Less. 1830, (teste Gray.J—In- 
fundibulum, D’ Ord. 1846, non Montf. 
This genus forms an exact transition in the shell from the 
spiral Crepidule to the Phoride, the animal of ; which is 
widely different. Itis in fact a Crepidula, with the anterior 
part shortened, while the posterior is lengthened. Several 
species might be ranked with either genus. It is represented 
in the Mazatlan collection by a single specimen. 
331. TRocHITA VENTRICOSA, 7. Ss. 
T. t. ventricost, subdepresst, irregulari; albidd, castaneo 
embuta; anfractibus i. |? aut pluribus] ventricosis, maxime 
prope suturam ad ang. 90° depressam ; superficie irregulariter 
noduloso-rugosa, rugis subobsoletis, diagonalibus, nodulis huc et 
tlluc prope suturam extantibus ; tot& pagind creberrime et 
minutissime corrugata ; epidermide lamellosd, corned, maxime 
prope marginem, indutd ; cavitate concavo ; lamina alba, lineas 
incrementi haud monstrantt, labio parum reflexo, umbilico nullo; 
margine forme sedis conveniente. 
Comp. Trochita radians, (Desh. teste H. & A. Ad. Gen. i. 367,) 
Dkr. Ind. Moll. Gain. p. 36, no. 97:=Trochus r. Lam. An. 
s. Vert. (ed. I,) vol. vu. p. 11, no. 5:— Schub. &y Wagn. 
Chemn. Suppl. pl. 229, f. 4063 :—=Calyptrea r. Zam. ed. 
Desh. vol. vi. p. 626, no. 8 :—=Infundibulum r. Zool. Beech. 
Voy. p. 148, pl. 39, f. 40, 11:—= Patella trochiformis, Chezmn. 
