YERTEBBATES. 359 



Hoene with especial reference to the stratigraphic range of the ichthyic 

 remains occurring therein. 



Position and locality : Warsaw beds; Boon ville, Missouri, and on the 

 Piasa, above Alton, Illinois. 



Chohaxodtts inceassattts, St. J. and W. 



PI. X, Fig. 18. 



Teeth of small size, seldom exceeding half an. inch in lateral diame- 

 ter, in outline linear, or slightly arched in the convex side, tapering 

 towards one or other extremity, both extremities obliquely truncated 

 from the convex to the concave border. The base is nearly vertical to 

 the crown, which it nearly equals in length and depth, very stout, com- 

 pressed and sharply denned beneath the coronal margins, expanded or 

 thickened below, the deep side slightly channeled laterally above, and 

 broadly beveled below, opposite side relatively low, deeply channeled, 

 inferior surface well-defined, very broad, plane, and strongly beveled to 

 inferior acute angle, in outline long-subrhomboidal as seen from the 

 deeper face, which is more or less strongly furrowed vertically. Crown 

 slightly exceeding the length and breadth of the base, the convex face 

 rising abruptly from the basal margin, gently arched vertically and lat 

 erally, crest compressed, culminating in an eccentric prominence near one 

 extremity, broadly arched towards the opposite end, the opposite face 

 descending in a broad, shallow concavity, which is limited below by a 

 strongly marked coronal baud composed of from three to five imbrica- 

 tions, which form a continuous band with that of the convex face, where 

 it is only about half as wide and composed of fewer imbrications; the 

 basal border in the convex face is nearly direct, sharply curved round 

 the lateral extremities and somewhat prominently defined from the basal 

 region; in the concave face, the basal border is strongly produced, the 

 median portion gently arched upward and inward, and sharply curved 

 to the extremities in the obliquely truncated lateral portions. The coro- 

 nal surfaces are polished and present a delicate vertical striation in the 

 lower portions ; on nearing the crest delicate vertical sulci often appear, 

 which produce a minute denticulation, and which is especially discerni- 

 ble in the convex side. 



Mr. Van Hoene has brought together a beautiful series of teeth from 

 the St. Louis beds, which we have been led to regard as the representa- 

 tives of a distinct form. At Alton and St. Louis these teeth are asso- 

 ciated with the G. insignia, Leidy, and a more slender form closely allied to 

 G. cultillus,~S. and W"., of the Chester limestone. The latter form also 

 occurs at the Pella (Iowa) locality, associated with G. inconstans, with 



