22 PROCEEDINGS OF THE ACADEMY OF 



CEPHALOPODA. 

 Genus SCAPHITES, Parkinson. 



SCAPHITES VENTRICOSUS. 



Shell ventricose, attaininga rather large size, oval-subglobose in form, broadly 

 rounded on the dorsum. Umbilicus very small, deep, and showing scarcely any 

 part of the inner whorls. Volutions about three to three and a half, increasing 

 rather rapidly in size, particularly in breadth, nearly twice as wide transversely 

 as from the dorsal to the ventral side; all regularly rounded on each side and 

 deeply embracing within ; last one deflected from the regular curve of the 

 others so as to become slightly disconnected at the aperture, which is trans- 

 versely reniform or lunate. Surface ornamented with numerous small, rather 

 regular costas, some forty-five to fifty-five of which may be counted around the 

 dorsum of each turn, where they are of uniform size, excepting their gradual 

 and uniform enlargement with the whorls. On the outer, or last volution, only 

 every fifth or sixth one of the costse extends across to the umbilical margin ; 

 the intermediate ones becoming obsolete on the sides, where those extending 

 entirely across become larger, more prominent and more angular than on the 

 dorsum. 



The septa are each provided with five deeply-divided principal lobes. The 

 dorsal lobe is longer than wide, and has on each side of its very slender body 

 three main branches, the two terminal of which are slightly larger than the 

 next pair above, and each provided with three or four small unequal subdi- 

 visions on the outer side. The dorsal saddle is as large as the dorsal lobe, 

 extremely narrow at its base and profoundly divided at its extremity into two 

 unequal branches, of which the one on the dorsal side is larger than the other, 

 and distinctly tripartite, each of its subdivisions being deeply sinuous and ob- 

 tusely digitate. The other main branch is very narrow, and provided with 

 several short, obtusely rounded, irregular lateral divisions. The superior 

 lateral lobe is as wide as the dorsal lobe, but shorter, and ornamented with 

 two large, nearly equal bifurcating terminal branches, the lateral subdivisions 

 of which are bifid and more or less digitate, while the other two are each pro- 

 vided with from five to seven digitations. The lateral saddle is much smaller 

 than the dorsal saddle, very narrow at its base, and consists above of two equal 

 trilobate terminal branches. The inferior lateral lobe is little more than one- 

 third as large as the superior, and very similarly divided, excepting that its 

 branches are proportionally shorter. The ventral lobe is very small and armed 

 with three or four short, simple divisions. 



Length, 313 inches; height, 2 65 inches; breadth or convexity, 1-90 inch. 



In its external ornamentation, this shell is much like a species described by 

 us from near the Black Hills, under the name of S. Warreni, (Proc. Acad. Nat. 

 Sci. Phila., May, 1860, p. 177.) It differs, however, remarkably in size and 

 form, being nearly twenty times as large, and proportionally much more ventri- 

 ccse, while its volutions increase much more rapidly in size. Its umbilicus is 

 also proportionally smaller and its body whorl not deflected so far from the coil 

 of the inner turns. As we have not yet had an opportunity to see the septa of 

 S. Warreni, we have no means cf knowing how nearly these foinis may agree 

 in their internal structure. 



Locality and position. Chippewa Point, near Fort Benton, on the Upper Mis- 

 souri ; Fort Benton Group of the Nebraska Cretaceous series. 



SCAPHITES VERMIFORMIS. 



Shell attaining a medium size, oval subdiscoidal in form. Umbilicus very 

 small. Volutions increasing gradually in size, rounded on the dorsum and 

 sides, and deeply embracing within; all a little broader transversely than from 

 the dorsal to the ventral side ; last one deflected from the regular curve of the 

 others, so as to become slightly disconnected at the aperture, which is trans- 



[Feb. 



