72 PALEONTOLOGY OF ILLINOIS. 



coronal ridge and the somewhat greater obliquity of the postero- 

 lateral border. As in the above example, the antero-lateral border 

 has a moderately oblique course from the obtuse inner angle out- 

 ward and forward, and is similarly marked by the produced basal 

 rim; the posterior depression, however, is quite obsolete, the slope 

 from the summit of the coronal ridge to the rounded fold along the 

 postero-lateral border showing scarcely the least transverse con- 

 cavity; on the other hand, while the gentler declivity in front is 

 faintly depressed, it is destitute of the impressed thread-like line 

 and narrow belt parallel with the anterior border observed in the 

 larger tooth. The surface punctation of the smaller specimens is 

 appreciably coarser and more like that of the associated teeth of 

 Psephodus, and in both the remnant of coronal enamel along the 

 inner margin is traversed by similar faint parallel lines of growth. 

 In the process of the preliminary distribution of the materials of 

 the collections for study, the teeth upon which the foregoing notices 

 are based were referred to Psephodus obliquus, a relationship 

 which may yet prove to be well founded the smaller of the examples 

 above referred to possibly representing the young stage of the large 

 teeth described under the latter designation. The latter specimen, 

 however, shows the inrolled extremity entire, instead of the oblique 

 truncation such as distinguishes all mature individuals of Psephodus, 

 while the strong inrollment and consequent strongly arched longi- 

 tudinal profile offer marked contrast with the forms of Psephodus 

 with which the present teeth were associated. The larger example 

 bears a striking resemblance to the mandibular posterior form of 

 Cochliodus', but of the latter genus no other remains have thus far 

 been discovered in Kinderhook horizons affording the teeth above 

 noticed. 



Geological' position and locality: Kinderhook formation ; Burling- 

 ton, Iowa. 



PSEPHODUS LATUS, ST. J. and W. 



PI. II, Fig. V3. 



Teeth small. Mandibular median (?) form sub-triangular in out- 

 line, moderately arched in the direction of inrollment. Antero" 

 lateral border nearly straight, undulated, the crenulated coronal fold 

 g harply inbeveled to the channeled basal portion; postero-lateral or 

 oblique border rapidly converging towards the outer extremity, making 



