224 MYTILUS, NAUTILUS. 
Sec. B. Convex or ventricose. Shell transverse ; 
hinge simple, destitute of teeth ; shell with three 
obsolete muscular impressions. ANopoNnTa of 
Bruguieres. 
cataractus, (toothless muscle,) shell thin, fragile, 
translucent, obiong-oval, convex ; covered with 
a radiated olive-green epidermis ; pearly with- 
in; beaks nearly central; front margin brown. 
Length about two inches anda half, breadth 
four and a half. 
marginatus, shell very thin, fragile, somewhat 
compressed, translucent, subovate ; epidermis 
olive-green, paler on the disk and greener be- 
fore ; anterior margin fuscous ; beak nearer to 
the posterior end; bluish-white within, edges 
whitish. 
See Ms. P. 
N. 
5—3. Nats. Spec. 10. 
proboscidea, with single lateral bristles and very 
long proboscis. Three-fourths of an inch long. 
In clear water an inch long. 
- serpentaria, body serpentine, with red spiral in- 
testines and triple black collar. In stagnant 
water. An inch long. 
wermicularis, without lateral bristles ; chin beard- 
ed. In stagnant water. One-sixth of an inch 
long. 
See MS. P. 
9—4. Navutitus. Spec. 31. 
pompelius, (nautilus,) aperture of the shell cor- 
date, with obtuse and smooth whorls. Pearly 
Within. 
See MS. P. 
