278 DESCRIPTION OF A COLLECTION OP POSSILS, 



obliquely; with very small, or entirely obsolete, umbilicus, and in having the colu- 

 mellar lip always thinly encrusted. In many respects they approach Amauropsis, 

 but they are more naticoid in style, rarely so elongate, and never have the spiral 

 sculpture, often found in that genus. AmpuUina, Faujas, 1803, of which the type 

 is A.fluctuata, is a heavy shell, with a peculiar incrustation of the inner lip, the 

 callus blending gradually into the outer surface. AmpulUna, Lam., 1813, was 

 proposed for the thin shells, with more or less of a carina bordering the umbilical 

 region, and which he had previously included in the fresh-water genus AmpuHaria. 

 For this genus the name of Eiispim, Agas., 1837, must be used, the type being 

 AmpuUaria sigaretina, Min. Conch., PI. 283, figs. 1-3. Glohularia, Swainson, 1840, 

 is also a synonym of this genus. Stoliczka, in Pal. Indica, incorrectly places some 

 species of our new genus in AmpulUna. Natica Pedernalis, Uoemer, Kreidebil- 

 dungen von Texas, may be taken as our type. A better figure than Roemer's will 

 be found in the Palseontology of California, vol. ii. PI. 35, f. 3. 



P. ovoiDEA, n. s., PI. 39, fig. T. 



Shell large, ovate, thin ; spire moderately elevated, whorls about five, sloping 

 above, not very convex; suture small; body whorl broadly convex, somewhat 

 oblique ; mouth sub-ovate, oblique, acute behind, broadly rounded in advance ; 

 inner lip encrusted by a thin layer. Surface marked only by lines of growth. 



Measurements. Length, 3.3 in.; greatest width of body whorl, 2.4 in.; length 

 of aperture, 2.5 in. The above measurements, except the width, are only approxi- 

 mate, since the extreme apex and the end of the aperture are imperfect. 



Locality/. Neighborhood of Ollon ; from a dark bluish limestone, different from 

 the matrix of the other Ollon specimens. Cretaceous (i). 



Remarks. This species is nearest to P. Pedernalis in form, but is more slender 

 and less oblique ; the spire is lower than P. prcsgrandis {Natica id., Roem.), also 

 from the Cretaceous of Texas, and probably Northern Mexico. It is of the type 

 ''Natica'' Elea, d'Orb., of the French Jura, at least so far as can be ascertained 

 from the back view given by d'Orbigny, but its spire is much lower. There is no 

 described species in South America approaching it in size, except P. prxlonga 

 {Natica, Seym.), from Brazil, Columbia, and France, and this has a spire as long as 

 the body whorl. 



P. INCONSPICTJA, n. s., PI. 39, fig. 8. 



Shell small, elongate ovate; spire very high ; whorls five and a half; rounded ; 

 upper surface rounded, sub-truncate ; body whorl broadly rounded in the middle, 

 sloping inwards below; aperture sub-circular; umbilicus absent, or very small; 

 inner lip very thinly encrusted. Surface smooth. 



