DOLABELLA. 151 



buccal tentacles slit above ; rhinophores or tentacles much nearer to 

 the anterior margin than to the dorsal slit, similar to those of Tethys. 

 Eyes minute, in front of rhinophores ; posterior area of body defined 

 by an obliquely transverse groove and ridge. Pleuropodial lobes 

 united except for a dorsal slit, more open at the ends, the anterior 

 insertions of lobes contiguous, parted only by the genital groove. 

 Mantle not nearly covering the gill, produced in a folded siphon be- 

 hind. Gill-cavity very large. Genital orifice under the posterior 

 part of gill, penis very long, near right buccal- tentacle. Opaline 

 gland multiple. 



Shell solid and calcareous, hatchet-shaped, loosely coiled, the free 

 spire obliquely decurved, heavily calloused; sinus deep and con- 

 cave ; margins reflexed. 



Type D. scapula Martyn. 



Distribution, tropical and subtropical Indo-Pacific and Australian 

 seas, and west coast of Mexico. 



Dolabella, while resembling Tethys in general appearance, differs 

 from that genus in several important respects. The epipodial lobes 

 are united behind and shortened in front, and their anterior ends 

 are contiguous (see pi. 66, fig. 14, dotted lines) ; the posterior part 

 of the body is marked off by a transverse ridge or frill ; the common 

 female orifice and vas deferens (pi. 66, fig. 14, g. p.} is situated far 

 backward under the hind part of the gill (fig. 14, G.) ; and corre- 

 sponding to this removal of the genital pore, the penis is greatly 

 lengthened. The shell is mainly calcareous, and has the spire free 

 and heavily calloused. 



The distribution of the genus is restricted compared with Teihys, 

 the Atlantic Ocean and communicating seas being without repre- 

 sentatives ; but the individual species seem to be more widely diffused 

 than in the other genus. Extreme points in the known distribu- 

 tion of the group are the Red Sea and Cape on the west, west coast 

 of Mexico, Sandwich and Viti Is. on the east ; and southward, New 

 South Wales is the limit. 



The species need revision further than that here attempted, as 

 there are several named forms of rather doubtful status. The shells, 

 with one or two notable exceptions, furnish only differential char- 

 acters of indifferent value. 



Synopsis of Species. 



a. Shell large, broad, with a saucer-like appendage above, gigas- 

 aa. Shell narrow, arched, the length about twice the width, 



[eloiigata. 



