298 LIOTIIDA. 
which is widest in the middle of the edge; nucleus obscure, 
punctured. 
PARIA, Gray. Shell elliptical, mouth wide; inner lip flat, 
shelving upwards, produced and truncated in the middle, with a 
roundish notch on ‘each side near the margin of the cavity. 
Operculum, shelly plate subquadrangular, lower edge straight, 
transverse, with a flexible flap, the upper edge with two tobes, 
the marginal lobe elongate, linear. 
STENOPOMA, Gray. Shell elongate; mouth elongate, narrow. 
Operculum oblong-elongate, the horny part triangular, very 
oblique, acute near the nucleus, and rounded at the end; shelly 
plate elongate, thin, with two elongated ridges on the upper end, 
the marginal one produced into a spine, with a notch on its left 
margin. 
ORTHOPOMA, Gray. Operculum oblong; horny part triangular, 
rather oblique; shelly plate half oblong, rather narrowed above, 
and rounded at the upper edge, with a very slight fold diverging 
from the nucleus to the left upper margin; the anterior carti- 
laginous flap large, broad. Shell unknown. 
The characters of all these divisions so run together through 
a series of specimens that they may be regarded as practically 
worthless. 
Veates, Montfort. 
Distr.—Tertiary.. V.perversa, Linn. (1xxviii, 81, 82). 
Shell oval-conic, spiral at the apex only; last whorl greatly 
enlarged, resembling Trochita in shape; aperture basal, semi- 
circular, forming with the wide flat, shelf-like columellar lip a 
circular outline ; columellar lip dentate. 
VELATELLA, Meek, 1878. Cretaceous and Laramie; United 
States. V. carditoides, Meek (1xxviii, 85, 86). 
PiLEoLUs (Cookson), J. Sowerby. 
Etym.—Pileolus, a little cap. 
Distr.—Marine; only known as fossils. 
Shell limpet-like above, with a subcentral apex; concave 
beneath, with a small semilunar aperture, and a columellar disk, 
surrounded by a broad, continuous peristome. 
The secondary species have the basis generally rounded and 
the apex subcentral, while the tertiary species have it more oval 
and the apex terminal; to the latter, approaching more nearly 
the recent Navicellz, Deshayes applies the subgeneric name 
romostoMa. P. radiatus, d’Orb. (1xxvili, 83, 84). 
Famity LIOTIIDA. 
Shell depressed spiral, white, ribbed, sometimes cancellate, or 
nodulous; aperture orbicular, rarely pearly within. Operculum 
corneous inside, outside having a calcareous coat formed of 
separate, pearl-like, shelly particles placed in spiral lines. 
