MAZATLAN UNIVALVES 339 



When adult, the canal is very short, and the labrum slightly 

 lirate within. Colour of a prevailing blackish brown, (brown 

 in the mouth,) variously dotted and marked with white. The 

 operculum is very minutely granular, and closely resembles 

 that of C. maculosum on a small scale. It differs from that of 

 C. stercus-muscarum in being of a lighter colour, thinner, with 

 the spiral part larger in proportion, margin more indented, 

 muscular scar smaller, scarcely marked. The smallest specimen 

 measures '035 by '027. The smallest adult, '45 by "2. The 

 largest, long. '6, long. spir. *35, lot. '28, div. 30. This is con- 

 siderably larger than Menke's specimen; but many of Prof. 

 Adams' were an inch long, and of Cer. no. 199, 1'2 long. 

 Hob Mazatlan ; rare ; L'pool Col. Taboga and Panama ; 

 extremely common, on and under rocks and stones, between 

 half-tide level, and low water mark of neap tides ; C. B. Ad. 

 Tablet 1602 contains 3 sp. extremely young, and an adult 

 with the operculum. 1603, a series of 7 sp. of different ages. 

 1604, 2 opercula. 



GENUS VEKTAGUS, Klein. 



H. fy A. Ad. Gen. vol. i. p. 285. Siphonal canal strongly 

 recurved ; columella plaited : operculum as in Cerithium, 

 (teste V. gemmatus, non teste Ad. fig.) ( 



M- 389. VEETAGUS GEMMATUS, Hinds. 



Cerithium gemmatum, Hinds, Voy. Sulph. Moll. p. 27, no. 104. 



pi. 11, f. 5, 6. C. JB. Ad. Pan. Shells, p. 152, no. 197. Sow. 



Tlies. Conch, sp. 17, pi. 177, f. 41. 

 Vertagus gemmatus, H. fy A. Ad. Gen. i. 285. 



This shell is very constant in its characters ; presenting a 

 sharp, straight outline, and a sculpture consisting of 3 rows of 

 nodules, (of which the upper is the larger,) with a double 

 spiral line between. The nodules are but slightly developed 

 in the young shell. There are numerous small varical ridges, 

 but only two principal ones, at the aperture, and at about two- 

 thirds of the last whirl. The siphonal canal in the adolescent 

 shell is short, and but slightly recurved: afterwards longer 

 and much bent. The posterior canal is thick, but with only a 

 slight groove. There is no parietal knob distinct from the 

 canal, and the columellar plait is very slight and sunken. The 



