MONOCBRO8. 



Genus MONOCEROS, Laiu. 



This small group is restricted in distribution to the Pacific 

 coasts of North and South America and the neighboring islands. 

 It is also represented in the tertiary of Chili. 



M. GRANDE, Gray. PL 60, figs. 288, 285-287. 



Brown externally, flesh-color within the aperture. 

 Length, 2'5-3'5 inches. 



The young shell has the ribs rounded, and not crossed by 

 scales. I have before me an extreme variety in which the spire 

 and canal are both produced and the ribs smooth. 



Length, 3'5 inches. 



M. MURICATUM, Brod. PL 60, figs. 290, 289. 



Yellowish or brownish ; aperture white or flesh-color, the 

 revolving raised lines usually darker. Length, 2*5-3 inches. 



Pi i m mi a to Mazatlan. 



Varies greatly in appearance ; the typical form having a very 

 much depressed spire and broad shoulder on the body, the whole 

 surface very scabrous, whilst an extreme variety, described by 

 Gray as M. tuber culo turn (fig. 289). has more elevated spire, the 

 surface not so scabrous, the ribs broken up into tubercles. 

 Carpenter, in his " Mazatlan Catalogue," refers this species to 

 Purpura, on account of the slight development of the horn in 

 the specimens which he studied; R. E. ('. Stearns (Am. Jour. 

 (7<wcfr.,vii, 170) facetiously remarks that this horn is sufficiently 

 prominent in his specimens " to enable the shell to enter the 

 genus Monoceros on its own hook. 1 ' This I can confirm. 



M. LUGUBRE, Sowb. PL 60, fig. 291. 



Yellowish brown, blotched or flamed with chocolate ; yellowish 

 brown within the mouth. Length, 1-2 inches. 



Pacific and Gulf Coasts of Lower California. 



Sowerby's is not the earliest published name for this species, 

 but it is so well known that it had better not be changed. 



