MAZATLAN UNIVALTES 231 



that of U. olivacea in being sharper at tlie outer edge, more or 

 less granular on tb.e ridges (in tlie young shell over the whole 

 surface), and with the small interior rib beginning within the 

 other. Its apex fits against t^e peripheiy of the shell. A very 

 finely grown spreading specimen measures long. 1' 2, lat.1'7, 

 (without the pahna; 1'36,) di v. 80". The largest, conical sp. 

 measures long. 1"73, lat. 1"8, (without the palma; 1'56,) div. 60". 

 Sab. — Mazatlan ; extremely abundant ; L'pool Col. — S. W. 

 Mexico, very fine, P. P. C. 



Tablet 1097 contains 5 sp. different ages, spreading variety.— 

 1098, 6 sp. do. ordinary form. — 1099, 3 do. conical.— 1100, 3 do. 

 scul]3ture clear. — 1101, 1 do. curiously mended after fracture. — 

 1102, 1 do. upper part eaten away, leaving the liver chamber 

 with the whu'ls disunited, like Vermetus. — 1103, 1 do. curiously 

 crowned with Coralline. — 1104, 1 do. covered with Alga;. — 

 1105, 2 do. bored by young Lithophagi. — 1106, 1 do. with large 

 Annelid, of which an operculum is added from a foU grown 

 sp. on Spondj^lus, distinguished by the two large and two 

 small branching stag's-horn processes. 



Specimens sJieioing base. Tablet 1107 contains 3 sp., pabnaj 

 broad, expanded. — 1108, 1 do. more distant.— 1109, 1 do. very 

 narrow. — 1110, 2 do. palma> numerous. — 1111, 3 do. iiTCgularly 

 developed. — 1112, 1 do. with labium narrowed by Sabellariae, 

 which, along with Bryozoa contending with Vermetidae for 

 superiorit>', have covered the base. — 1113, 1 do. with base 

 cui'iously rounded. — 1114, 1 do. mouth blistered. — 1115, 1 do. 

 with attachment of Calyptraid outside the basal edge of the 

 mouth. 



Tablet 1116 contains 2 sp. with the opercula in situ, one 

 young, the other adult. — 1117, 6 opercula. 



Genus TEOCHUS, Linn. 



Trochus, Linn., auct, pars ■.—Phil. Hand. Condi, p. 210. The 

 ancient name is retained for these, the ordinary forms of the 

 original genus. 



Ziziphinus, Leach :—H. Sf A. Ad. Gen. vol. i. p. 421 -.—Mon. 

 in Proc. Zool. Soc. 1851, p, 163. 



289. Tfiocnrs veesicoloe, ]in:e. 



Zeit. f. Mai. 1850, p. 172, no. 32. 



?=Ziziplunus Californicus, A. Ad. Proc. Zool. Soc. 1851, p. 168, 

 no. 52. 



