86 PALAEONTOLOGY OP ILLINOIS. 



the downward and slightly outward produced basal rim. A medium 



sized tooth measures between the angles of the inner margin 5 



m m, and about the same as the length along the antero-lateral 

 border. 



Geological position and localities : St. Louis formation : St Louis, 

 Mo., Alton, 111., Pella, Iowa. 



VATICINODUS? SIMILIS, St. J. and W. 



PI. IV, Fig. 17-19. 



Maxillary posterior teeth very small, subspatulate in outline, very 

 obliquely inrolled. Antero-lateral border with moderate obliquity 

 outward and forward, coronal fold very narrow and inbeveled to the 

 shallow, channeled basal rim ; postero-lateral border slightly arched, 

 basal portion channeled and limited above by the inbeveled coronal 

 fold, posteriorly expanding beyond the coronal border terminating 

 in the sharply-rounded posterior extremity; inner margin abruptly 

 and deeply arched from the posterior angle round the base of the 

 coronal prominence, thence more gently curved to the obtuse 

 anterior angle. Coronal prominence occupying about half the 

 entire area of the crown, moderately and regularly arched trans- 

 versely, culminating in the low rounded crest near the anterior 

 side where it is more or less well defined from the plain anterior 

 area into which the slope merges. Surface closely and finely punc- 

 tate, the anterior region showing faint revolving plicae. Breadth 

 between the angles of the inner margin about 9 m m. ; length 

 along antero-lateral border probably 3mm. A large tooth 

 measures 22 m m. across the inner margin, and 6 m m. at the 

 antero-lateral border. 



With the above described form occur teeth referable to the opposed 

 position on the lower jaw, and which may have been associated 

 with them. These teeth might readily be mistaken for worn 

 examples of the mandibular posterior teeth of Deltopty chins, which 

 they closely resemble in outline and contour of the coronal region. 

 The specimen figured presents the usual appearance of the form, 

 which has a triangular outline, the antero-laterai border slightly 

 curved, with abrupt mural face, half or more of its height envel- 

 oped in the enamel belt which is distinctly defined from the slightly 

 flaring basal rim; inner margin nearly at right angles with the 

 anterior border, broadly arched in a slight sigmoidal course passing 



