344 MAZATLAN UNIVALVES 
the columellar lip. The apex is always more or less decollated ; 
fresh septa are made within; and the unused portion left to 
rop off or not according to circumstances. The shell is never 
inecrusted. The operculum has about 15 whirls, with a very 
tnin loose edge ; it igslightly rugulose and concave externally, 
and very glossy within. The smallest of the adult specimens 
measures long. °88, long. spir.'6, lat.°4, div. 25°. 
The broadest (7 whirls) ,, 1°33, ye Dire. ew 4s 5, keo 
The narrowest alo. be Os 252, 47,, 2o°. 
These measurements are exclusive of the labrum, which 
measures in one specimen fat. 12, alt. ‘24. 
Hab.— Guayaquil, D’ Orbigny.—Panama; not uncommon, half 
buried in muddy sand under bushes at high water mark ; 
C. B. Adams.— Mazatlan ; abundant; L’pool & Havre Coll. 
Tablet 1617 contains 6 sp. in different stages of growth; one, 
being broken, shews the extreme thinness of the shell, and 
the axis.—1618, 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. — 1624, 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 
opercula. 
395. CERITHIDEA P vaRIcosa, Sow. var. MAZATLANICA. 
Cerithiim varicosum, ?Sow. Gen. f. 5.—Kien. Icon. Conch. 
p. 94, no. 77, pl. 30, f. 2.--? Rve. Conch. Syst. vol. i. p. 178, 
pl. 226, f. 5.— Desh. in Lam. An. s. Vert. vol. ix. p. 321, 
no. 60.— B. M. Cat. D’ Orb. Moll. p. 48, no. 373.— Sow. 
Thes. Conch. p. 887, sp. 169, pl. 186, f. 280-2.—? Val. Rec. Obs. 
vol. 1. p. 282. 
Cerithidea varicosa, Mon. loc. cit. p. 83. 
=Cerithium validum, C. B. Ad. Pan. Shells, no. 206, pp. 157, 
310. 
C.t. “C. varicose, Sow.” simili ; sed minore, gracili, unicolore, 
atro-fuscd ; anfr. ultimis haud subito crescentibus ; tolumelld 
viz tortuosd; labio haud incrassato ; costulis spiralibus, anfr. 
penult. plerumque iv. (ili.—v.), liras transversas parum arcua- 
tas transeuntibus, ad interstitia nodosis ; varicibus valde irregu- 
laribus. 
