344 MAZATLAN UNIVALVES 



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

 fresh 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 glossy within. The smallest of the adult specimens 

 measures long. '88, long. spir. '6, lot. *4, div. 25. 



The broadest (7 whirls) 1'33, '9, 74, 28. 

 The narrowest 1'3, '92, '52, 23. 



These measurements are exclusive of the labrum, which 

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

 Hob. Guayaquil, _D' Orbigny. Panama not uncommon, half 



buried in muddy sand under bushes at high water mark ; 



C. B. Adams. Mazatlan ; abundant ; IS pool Sf Havre Coll. 



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

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

 the aids. 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. 



I 395. CEEITHIDEA FVAEICOSA, Sow. var. MAZATLANICA. 



Ceritjiium varicosum, ?Sow. Gen. f. 5. Kien. Icon. Conch. 

 p. 94, no. 77, pi. 30, f. 2. ?Rue. Conch. Syst. vol. ii. p. 178, 

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

 no. 60. JB. M. Cat. D'Orb. Moll. p. 43, no. 373. Sow. 

 Thes* Conch, p. 887, sp. 169, pi. 186, f. 280-2 ? Vol. Eec. Obs. 

 vol. ii. p. 282. 



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



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

 310. 



C. t. "C. varicosce, Sow." simili ; sed minore, gracili, unicolore, 

 atro-fu$cd ; anfr. ultimis hand subito crescentibus ; columelld 

 vix tortuosd ; labio hand incrassato ; costulis spiralibus, anfr, 

 penult, plerumqua iv. (iii. v.), liras transversas parum arcua- 

 tas transeuntibus, ad interstitia nodosis ; varicibus valde irregu* 

 laribus. 



