MAZATLAN UNIVALVES " 487 
Genus NITIDELLA, Swains. 
Nitidella, Swazns. (shell.)—Nitidella, Gray, (operc.) 
Buecinum, pars, Lan. 
Columbella, pars, auwet. 
Testa ut in Mitrelia (Risso, non Swains. H. & A. Ad. Gen. 
vol. 1. p. 183 ;) énterdum decollata ; labio continuo, haud crenato. 
Operculum elongatum, nucleo laterali, ut in Purpurd formatum. 
The operculum of the following species being distinctly 
Purpuroid, it is necessary to remove it from both Buccinum 
and Columbella; and as none of the genera in Purpuride 
seemed constituted so as to receive it, the above name (given 
by Swainson from the shell alone) was adopted by Dr. Gray 
for such of the Columbelle as might prove to have Purpuroid 
opereula. It did not seem expedient to adopt the group 
of Messrs. Adams, till the opercula of other species had been 
examined ; nor to draw out a more precise diagnosis, till it 
was known how far the peculiarities of B. cribrarium were of 
specific or of generic value. 
613. NITIDELLA CRIBRARIA. 
Buccinum ‘cribrarium, Zam. An. s. Vert. vol. x. p. 176, 
no. 43.—Quoy & Gaim. Voy. dev Astr. Zool. vol. ii. p. 421, 
pl..30, f. 21, 22.— Kien. Icon Conch. p. 45, no. 44, pl. 16, f. 57. 
Columbella cribraria, Sow. Thes. Conch. p. 129, no. 51, pl. 37, 
f, 112, 113.—Desh. in Lam. loe. cit.—Gray in Zool. Beech. 
Voy. p.129.—B. WM. Cat. Cub. Moll. p. 27, no. 316.—Mke. 
(Conch. St. Vine.) in Zeit. Ff. Mal. 1853, p. 75. 
(Columbella) Mitrella cribraria, H. & A. Ad. Gren. i. 183. 
= Voluta ocelata, Gimel. p. 3455. 
=Le Barnet, Adans. Seneg. p. 146, pl. 10, f. 1. 
=Buccinum parvulum, Dkr. in Zeit. f. Mal. 1847, p. 64.— 
Phil. Abbild. iu. pl. 2, f. 7. 
=C. mitriformis, Brod, & King, Zool. Journ.—Lister, Conch. 
pl. 929, £.24, (teste Gray.) 
=C. guttata, Sow. Proc. Zool. Soc. 1832, p. 118,—Miill. Syn. 
Nov. Test. Viv. p.88.—C. B. Ad. Pan. Shells, p. 89, no. 89.— 
(Non Sow. Proc. Zool. Soc. 1844, p. 50: — Thes. Conch. 
p. 181, no. 59, pl. 39, f. 124:=C. punctata, do. index, p. 146.) 
This well marked form appears to be very widely diffused. 
The Pacifie type is of course regarded by Prof. Adams as 
distinct from the Caribbzxan, as it was at first by Sowerby. It 
