138 Panama Shells. MURICIDJE. 



the species were represented by few individuals, at least so far 

 as they could be found without a dredge. A similar abundance 

 of species and scarcity of specimens in this genus occurs in the 

 Caribbean seas. One large species was found ; of the others, 

 nearly one half are as small as the Caribbean species : the rest 

 are nearer to an average size as compared with the species which 

 have been described by European authors. Most of the small 

 species are undescribed. If we may judge from the collections 

 made by us in Panama and in Jamaica, and received from Cey- 

 lon, it may be conjectured that the undescribed species in this 

 genus are as numerous as those which have been described. 

 We do not refer to Kiener's monograph, which contains 60 spe- 

 cies : for, including the allied genus Mangelia, nearly 500 species 

 have been described. Probably this is not more than half of 

 the number actually existing. 



163. Pleurotoma aterrima. 



Synonymy. 



Pleurotoma aterrima Sowb. in Proc. Zool. Soc. Lond. 



p. 137. - - Dec. 1833. 



Mull. Synop. Nov. Test. Viv. p. 113. May 1836. 



Reeve Conch. Icon. pi. 12. f. 100. May 1843. 



Station. Under stones ; Cuming ! Eeeve. 

 Our living specimens were found in the same situation at low 

 water mark. 



Habitat. Monte Christi ; Cuming ! Sowerby : also Eeeve. 



West Columbia ; Jay. 



Panama ; C. B. A. ! 



We collected 14 specimens, most of which were occupied by 

 hermit crabs. 



164. Pleurotoma atrior. Nov. sp. 



Shell subfusiform : jet black, with a paler translucent spiral 

 stripe below the middle of the whorls : with a spiral series of 



