82 MUREX. 



dimensions nor distinctive characters (nearly all the species pub- 

 lished by him in this paper are similarly indefinite), so that it is 

 impossible to ascertain what species he intended to describe ; the 

 description itself, however, as far as it goes, will characterize 

 very exactly our present species, and such being the case, I have 

 a right to so identify it. 



M. MOTACILLA, Chemn. PL 12, figs. 129, 131 ; pi. 13, figs. 132-134. 

 There are usually two prominent longitudinal tubercles be- 

 tween the varices instead of three, as in the last species. The 

 surface is closely covered with revolving lines which become 

 tuberculous on the elevations, and here and there slightly spinous. 

 The canal is very narrow, and turned to the right. There are 

 two or three brown bands, usually. 



Length, 2*5 inches. 



Senegal, West Indies. 



This species is rather variable, and presents, among others, 

 two forms which may retain the specific names given them, as 

 varieties : 



VAR. CAILETI, Petit. Figs. 131, 132. 



Shell smoother, more angulated on the periphery, more spinous, 

 the nodules smaller, forming two or three ribs or tubercles between 

 the varices. The principal revolving lines are colored brown so 

 that the surface appears variegated with revolving, narrow, thread- 

 like bands. I figure a specimen from the original lot collected 

 by M. Caillet, which is much more angulated than the type^fig. 

 131) and I have before me a fine series of intermediate forms. 



VAR. ELEGANS, Beck. Figs. 133, 134. 



Longitudinal tubercles two between the varices, prominent, 

 spines not developed, periphery only obtusely angulated, the 

 raised revolving, thread-like lines dark-colored. This is a very 

 beautiful variety which may include as a synonym M. trilineatiis, 

 Reeve, (fig. 134). 



M. CHRYSOSTOMA, Gray. PL 13, figs. 136, 135. 



In general appearance not unlike M. motaciUa, Yar. elegans, 

 this species presents the following distinctive characters, which 

 appear to be permanent : it is larger, stouter, the canal is pro- 



