GENUS DOLIUM. 13 
these ribs are separated from each other by a shallow furrow, 
which becomes wider between the first two or three upper 
ribs, by the disappearance of the intermediate ribs. ‘The lon- 
gitudinal strie of growth are numerous, very fine, and slightly 
apparent. The aperture is narrow, for it is much contracted 
by two protuberances situated upon the two lower thirds of 
the columella. The right lip is arched, flattened, widened 
within, having a wide longitudinal ridge outside of it; it has, 
on the inside, the whole length, from sixteen to eighteen 
ridges, or very strongly prominent teeth. ‘The edge is un- 
dulated and denticulated. The left lip is thin, diaphanous, 
spreading upon the body of the shell, to which it adheres, 
except towards the base, where it becomes free and thicker. 
The columella is twisted, and presents a very deep emargina- 
tion, above which is seen a wide, thick, furrowed tubercle, 
which appears as if suspended over this hollow; another 
tubercle projects near the base, separated from the first by 
the cavity just spoken of; it is furnished with wrinkles and 
numerous furrows of a brilliant white, which imperceptibly 
diminish in size at the base, and above the emargination, 
which is turned out like a gutter, and perfectly smooth. The 
color of this shell is whitish, slightly blended with a dull 
yellow. The interior is red. The epidermis is thin and 
yellowish. 
Length 5 inches. Width 4 inches. 
Inhabits the South Sea, the Pacific Ocean, the coast of 
Mexico, at Acapulco. 
This shell, which becomes often very large, and which is still 
quite rare in collections, is that which Valenciennes has de- 
scribed under the name of Matea Jatilabris (Recueil d’ Obser- 
vations de Zodlogie, Humb. et Bonpl. p. 325). It is exceedingly 
remarkable for the development of the right lip, which is wide 
and provided with strong teeth throughout its whole length. 
The form and the situation of the two tubercles which pro- 
ject from the columella are also very singular, and concur to 
