490 MAZATLAN UNIVALVES 
itself being very variable in shape, sometimes rather elongated, 
sometimes squarish. The muscular scar occupies the inner 
portion, long and narrow. A large specimen measures ‘22 by 
"14, and therefore can only make its egress from the adult 
mouth sideways. This is provided for in the narrow scar, and 
accounts for the frequent decollation of the apex.—In many 
hundred specimens however, the nucleus was.found to be ab- 
normal, generally near the middle of the oufer margin, as in 
Bueccinum undatum ; but often nearly central. So common is 
this state that great confusion might have arisen if the oper- 
cula had been first described from only a few specimens. 
The smallest adult shell measures °82 by °47; the largest 
specimen long. 1°3, long. spir. °58, lat. °84, div. 80°. 
. Aslendersp. ,, 1°l, < AG) ee Be Oe. 
A broad sp. - °94,, te aoe ho Ope dy aOUE. 
Hab.—Isle Muerte, Cuming.—Seas of 8. America, Deshayes.— 
Panama, Col. Jewett.—Taboga, rare, C. B. Adams.—Mazat- 
lan, Melchers, Lieut. Green. — Do. ; extremely abundant 
and fine; L’pool Col. 
Tablet 2310 contains 7 sp. very young.—2311, 6 do. a stage 
older, aperture not contracted.—2312, 5 do. aperture contract- 
ing.—2313, 4 do. labral ridge just appearing.—2314, 5 do. 
teeth commencing.—2315, 5 do. mouth almost complete. 
Tablet 2316 contains 6 sp. adult, broad form.—2317, 6 do. 
normal state.—2318, 6 do. more elevated.—2319, 6 do. acumi- 
nate.—2320, 3 do. with opercula in situ. 
Tablet 2321 contains 3 sp. var. minor, broad.—2322, 4 do. 
normal.—2323, 3 do. acuminate. 
Tablet 2324 contains 3 sp. epidermis removed.—2325, 3 sp. 
shoulder pinched.—2326, 4 sp. incrusted with Bryozoa, &e.— 
2327, 3 sp. mended after fracture. 
Tablet 2328 contains 12 opercula, normal.—2329, 6 do. in- 
crusted with Bryozoa, Annelids, &c.—2330, 6 sp. nucleus near 
the center of theouter margin.—2331, 6 do. nucleus nearer the 
center of the operculum.—2332, 6 do. nucleus almost central.— 
2333, 5sp. of strange shapes through fracture.—2334, 3 do. 
with layers composed of different elements. 
616. CoLUMBELLA STROMBIFORMIS, Lam. 
An. s. Vert. ed. Desh. vol. x. p. 266, no. 1.—Sow. Gen. f. 1 :— 
Thes. Conch. p. 110, no. 1. pl. 36, f. 1, 2.— Val. in Rec. Obs. 
