70 [March, 



Descriptions of new sjjccies of Gasteropoda and Cephalopoda from the Cretaceous for- 

 mations of Nebraska Territory . 



By F. B. Meek and F. V. Hayden, M. D. 



TuRRiTELLA CONVEXA. Shell acutelv couical ; rolutions flattened convex ; su- 

 ture linear, indistinct; surface marked with fine lines of growth; aperture 

 ovate, acutely angular above, rounded below. Length unknown; breadth 

 of largest specimen .39 inch ; apical angle very convex, divergence 20. 



This species may at once be distinguished from any other shell known to us 

 from this region, by the convexity of the lateral slopes of the spire, and the 

 absence of revolving lines. 



Locality and position. Yellow Stone river, one hundred and fifty miles from 

 mouth. No. 4 of the series. 



TuRitiTELLA MoREAUENSis. Shell terete; spire elevated; volutions (number 

 unknown) flattened, increasing very gradually from the apex, and ornamented 

 by elevated thread-like revolving bands or lines about equal the intermediate 

 spaces ; while sharply elevated, regular, and somewhat distant, lines of growth 

 traverse the whorls fn the other direction : suture linear and sharp ; aperture 

 subquadrate, forming nearly a right angle on the inner side above, and termi- 

 nating in a distinct notch on the columellar side below. Length (unknown,) 

 breadth .10 inch; length of aperture .07 inch, breadth .04 inch; apical angle 

 regular, divergence 9". 



We have only incomplete specimens of this species, consisting of from six to 

 eight volutions, of which there were probably not less than ten. On the last 

 whorl, there is a fourth smaller revolving line below the others, and still lower, 

 several very fine revolving stria;. The lines of growtli, are much more distinct 

 between, than upon the revolving lines on all parts of the shell. 



Locality and position. Moreau river. No. 5 of the series. 



Belmnitella? bulbosa. Shell elongated, cylindrical, widening at the open- 

 ing, then somewhat contracted, and again enlarging below the middle, whence 

 it gradually tapers to a point; alveolus having a small groove down the dor- 

 sum, and marks of transverse septa round the sides ; substance of the shell 

 fibrous, fibers radiating at nearly right angles from the central linear axis to 

 the exterior. Phragmacone tapering regularly at an angle of 20 from the 

 larger extremity to the apex, where it terminates in a minute but distinct bulb- 

 like expansion; section circular or broad oval, septa faintly sinuate on the 

 dorsum and separated by spaces equalling about one-sixth the diameter of the 

 shell ; about twenty-eight of the septa may be counted in the space of half 

 an inch from the apex. Length unknown ; diameter of largest fragment .33 



inch. 



We have of this species perfect specimens of the phragmacone, but having 

 onlv seen longitudinal sections, and worn fragments of the external horny shell, 

 we'know nothing of its surface markings, nor whether or not it possessed the 

 longitudinal slit'characteristic of the genus. The groove down the inner side 

 of the alveolar cavity, however, is well marked in some of the fragments. We 

 were at first inclined to refer it with doubt to Belmnitella mucronata (D'Orb.) 

 which has already received such a multiplicity of names, but a careful com- 

 parison with authentic specimens of that species from New Jersey convinces us 

 it is different, and may be at once distinguished by the small bulb at the 

 apex of the phragmacone, which always leaves its impression at the point of the 

 alveolar cavity. So far as we know, this genus is, in the old world, confined to 

 the true chalk. 



Locality and position. Moreau river. No. 5 of the series. 



Ammonites halli. Shell large, laterally compressed, rounded on the dor- 

 sum ; umbilicus rather small, deep, somewhat funnel shaped, exhibiting one- 

 third to one-fourth, of each of the inner volutions; surface ornamented by 

 numerous small, slightly elevated, costie, which cross the volutions more orless 

 obliquely. About one-fourth of those crossing the dorsum reach the umbilicus, 



