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 pl. 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 (pl. 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 Tethys, 
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, 
[ elongata. 
