314 MAZATIAN TTNIVALVES 



the coluraellar lip. The apex is always more or less decollated : 

 fresli septa are made within ; and the unused portion left to 

 drop off or not according to circumstances. The shell is never 

 incrusted. The operculum has about 15 whirls, with a very 

 thin loose edge ; it is slightly rugulose and concave externally, 

 and very glossj- within. The smallest of the adult specimens 

 measures long. '88, lo7ig. spir. '6, lat. '4s, div.25°. 



The broadest (7 whirls),, I'SS, „ '9, „ '74, „ 28". 



ThenaiTOwest „ IS, „ '92, „ '52, „ 23°. 



These measurements are exclusive of the labrum, which 

 measures in one specimen lat. '12, alt. '24. 



Sab. — Guayaquil, D'Orhigny. — Panama; not uncommon, half 

 buried in muddj^ sand tmder bushes at high water mark ; 

 C. B. Adams. — Mazatlan ; abundant ; L'pool Sf Havre Coll. 



Tablet 1617 contains 6 sp. in diflereut stages of growth ; one, 

 being broken, shews the extreme thinness of the shell, and 

 the axis. — IGIS, 5 sp. adult, dwarf state. — 1619, 5 sp. normal 

 state. — 1620, 3 do. ribs somewhat obsolete. — 1621, 5 sp. elong- 

 ated. — 1622, 1 do. shewing sutural line. — 1623, 2 sp. later ribs 

 subgranulous, normal form. — 1621, 3 do. elongated. — 1625, 

 1 sp. with two contiguous varices. — 1626, 1 sp. very thick 

 varix. — 1627, 1 sp. with operculum in situ, and two separate 

 opercida. 



395. Ceeithidea ? vaeicosa, Sow. var. Mazatlanica. 



Cerithium varicosum, ?Sow. Gen. f. 5. — Kien. Icon. ConcJt. 

 p. 94, no. 77, pi. 30, f. 'i.—?Rve. Conch. Si/st. vol. ii. p. 178, 

 pi. 226, f. 5. — Desh. in Lam. An. s. Vert. vol. ix. p. 321, 

 no. 60.— 5. M. Cat. D'Orh. Moll. p. 43, no. 373. — Sojc. 

 Thes. Conch, p. 887, sp. 169. pi. 186, f. 280-2.—.? Val. Bee. Obs. 

 vol. ii. p. 282. 



Cerithidea varicosa, Jfon. loc. cit. p. 83. 



= Cerithium validum, C. B. Ad, Pan. Shells, no. 206, pp. 157, 

 310. 



C. t. "C. varicoscB, Sow." simiU ; sed minore, gracili, unicolore, 

 at7'o-fusca ; anfr. ulthnis hand siibito crescentibu^ ; columella 

 vix tortu^sa ; labio hand incrassato ; costulis .tpiralibus, ar\fr. 

 ■penult, plerumque iv. (iii. — v.), liras transversas parum arcua- 

 tas transeuntibus, ad interstitia nodosis; vai'icibus valde irregu- 

 luribus. 



