390 DESCRIPTIONS OF NEW SPECIES OF FOSSILS, 



which are crossed by fine, slightly undulating, sub-equal, revolving lines, presenting 

 under the magnifier a beautiful cancellated appearance. Aperture oval, approaching 

 sub-ovate, narrower above, oblique ; outer lip thin ; pillar lip not thickened ; umbilicus 

 obsolete ornone. Spiral angle 57°. Length (of largest specimen), .9 inch; breadth, 

 .6 inch. Last volution, .6 of whole length. 



This shell resembles very closely the N. cassisiana of D'Orbigny, (Terrains Cretaces, 

 p. 166, pi. 175, figs. 1-4,) but diffiers in its more acutely elevated spire. The surface 

 markings are also quite different, the lines of growth being regular and distinct, while 

 the revolving lines are not punctate, as in D'Orbigny's species ; and the aperture of 

 the latter is proportionally wider below. In general form this species approaches 

 the N. Clementina and N. Javigata among the Cretaceous species, and several Oolitic 

 species figured by D'Orbigny, Pal. Francaise, Terrains Jurassiques. 



Locality and Position. — Great Bend of the Missouri Eiver and Sage Creek, division 

 No. 4 of the Section. 



ACTEON CONCINNUS, il. Sp. 

 Plate III. Fig. 4, a-d. 



Shell globose or sub-oval ; spire very short ; volutions three and a half to four ; 

 suture narrow, but distinct ; surface brilliant, with a porcelain-like polish, and orna- 

 mented with about thirty equidistant punctate revolving grooves or striae. Aperture 

 narrow, semilunar, contracted at the posterior extremity, rounded in front. Columella 

 with one strong fold at the base, and a broad, deep spiral depression aboA'e it. Spiral 

 angle about 100°. Length, .17 inch; breadth, .15 inch. The last volution .88 of 

 whole length. 



Locality and Positiofi. — This beautiful little species is found at Sage Creek, in con- 

 nection with Baculites ovatus, B. compressus (Say), Scaphites nodosus (Owen), &c. 

 Also at Great Bend of the Missouri. In the upper and lower parts of ?fo. 4 of 

 Section. 



BUCCINUJ1 1 VINCULUM, 11. Sj). 



Plate III. Fig. 5, a, i. 



Shell below the medium size, elongate-ovate ; spire moderately elevated ; volutions 

 about five or six, convex, regularly rounded ; suture strongly impressed ; surface 

 marked by numerous strong longitudinal folds, and at irregular intervals with strong 

 varices ; fine lines of growth parallel to those ridges cover the entire sui^face ; these 



