PT-EROPODA. 491 
obliquely rounded ; posterior surface covered with serratures in lines 
from the mouth to the margin; and along a line from the mouth to 
outer margin is a series of vibrating cilie; basal lappet short and 
broad, emarginate at tip. Viscera within the tube much as in the 
preceding species, except that the dark mass is grass-green. 
SHELL very strongly recurved, forming nearly a quarter of a circle; 
aperture circular. 
Length not over half an inch. 
Taken by Mr. Dana between Oregon and the East Indies. 
The extraordinary curvature of the shell is a prominent character- 
istic, as well as the peculiar form of the wings. 
Figure 608, the shell, with the animal, enlarged. 
The four following species of Atlanta do not belong in this group, 
but their affinities are with the Gasteropoda, and they are allied to 
Janthina. Indeed, Mr. J. EK. Gray has proposed a family, including 
them, under the name Janthinide. ‘The original figures were inad- 
vertently laid aside among those of Pteropoda, with which they have 
been sometimes ranked. 
ATLANTA PRIMITIA (Gould). 
T. nautiloidea, rotundato-ovata, compressa, dextrorsum umbilicata, ca- 
rind lata sensim angustata cincta: spira anfractibus tribus : apertura 
angusta, elliptica, angulis acutis ; labro arcuato ; color violacea. 
Anta having the mouth at the extremity of a long proboscis, and 
at times dilating like a sucker, with a fissure or emargination at its 
superior side, and fringed with ciliz in incessant motion. Eyes very 
large, at the distal third of the protruded body ; they are vitreous, and 
situated on short, black peduncles; between them is a prominence, or 
forehead, advancing a little in front of them, on each side of which 
arises a fleshy, fusiform tentacle. From the base of the proboscis, on 
