MAZATLAN URIVALVES 223 
Emarginula. The plan of cancellation and the form of the shit 
differ somewhat in the specimens, but probably not specifically. 
The smallest shell, though scarcely ‘04in length, displays a 
channel ‘01 long, as in the adult. The largest measures 
tong. °125, lat. ‘O07, alt. *035. 
Hab.— Mazatlan; on Spondylus calcifer, extremely rare ; 
L’pool Col. 
Tablet 1080 contains 3 sp. of different ages. 
Famity HALIOTIDZ. 
Nihil. 
Famity TROCHID. 
Gents CALLOPOMA, Gray. 
Fig. Moll. An. p. 87, no.5:—Phil. Handb. Conch. p. 206 :— 
Hi. & A. Ad. Gen. i. 395. 
Turbo, sp., auct.—Distinguished by the extreme complexity 
of the operculum : z. infra. 
282. CatLtopoma (Turso) FrLUuctvosum, Mave. 
Turbo fluctuosus, Gray in Wood Suppl. p. 20, pl. 6, no. 44.— 
Mike. Zeit. f. Mal. 1847, p. 179, no. 8: —do. 1850, p. 170, 
no. 25.—Kust. Chemn. p. 60, no. 55, pl. 14, f. 3, 4 e. 
Turbo fluctuatus. Rve. Proce. Zool. Soc. 1848, p. 52 — Conch. Ic. 
sp. 34, pl. 8, no. 34. 
Trochus (Turbo) Fokkesii, Jonas, in Phil. Abbild. no. 1, pl. 2, 
f. 1, 10.—Midden. Mal. Ross. pt. ii. p. 86. no. 13. 
Callopoma fluctuatum, H. § A. Ad. Gen. 1.395, pl. 43, £.7, 7a, 7. 
Comp. Callopoma ?fluctuatum, var. depressum, Proc. Zoo!. 
Soe. 1855. (= Turbo f. var. Rve. Conch. Ic. pl. 9, £.3 c.)=Turbo 
funiculosus, Aven. Icon. Conch. pl. 30, f. 1. 
Almost all the numerous specimens of this beautiful shell 
fell victims, after I had first examined them, to the grindstone 
and acid. The exquisitely beautiful opercula were however 
thrown to one side as useless, andso preserved. These are flat 
and covered with a dark horny layer inside, displaying about 6 
whirls. Outside with a broad central spiral callus, white and 
granular, concealing the umbilicus, with extremely minute 
pustules over the surface, sometimes with a few sharp prickles. 
A deeply cut groove surrounds the callus, followed by a green 
