PTEROPODA. 493 
Anima of a pale-flesh colour, with a slender neck: the proboscis 
about as long as the neck, uniting with it at an angle of about 
130°, and presenting something like an elevated forehead between the 
eyes. At its extremity is the mouth, which soon dilates into a large 
cesophagus, or stomach, from which a distinct alimeutary canal passes. 
The eyeball is crystalline, with a dark spot like a peduncle, at the 
base of which lies the brain; at the junction of the natatory membrane 
with the neck is a nervous ganglion, from which nerves pass in 
various directions. The natatory membrane is elongated, tongue- 
shaped, covered with cilie; its marginal appendage, which is pro- 
bably an instrument for adhesion, is kidney-shaped. The foot, or 
opercle, is narrow, ovate. The pulsating organ is ovate, of an ochreous 
colour; the viscera within the spire of the shell are convoluted and 
straw-coloured. Mantle conspicuous, of the same colour. 
SHELL very delicate, with a keel nearly as broad as the shell itself, 
nearly circular, compressed, quite simple, merely exhibiting very faint 
lines of growth. 
Obtained by Mr. Dana in latitude 28° N. long. 178° E., to the 
westward of the Sandwich Islands. 
This animal is quite different from the preceding, and is unlike any 
species hitherto figured. It is described from the figures and notes of 
Mr. Dana. The anatomical details are well delineated. 
Figure 198, the animal and shell, enlarged; 198 a, the head, still 
more enlarged; 198%, the cervical ganglion and its branches; 198, 
natural size. 
ATLANTA VIOLACEA (Gould). 
1’. nautiloidea, vix compressa, violacea, valde carinata: anfractus qua- 
tuor sensim crescentes : apertura elliptica, angulis rotundatis. 
SHELL violaceous, nautiloid, whorls four, the last volution not 
rapidly enlarging, and unusually distended; keel nearly as broad as 
the whorl at the aperture, which is elliptical, about twice as long as 
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