300 TRANSACTIONS OF THE [maR. 15, 



transverseh', gently arched longitudinalh', ends rounded ; sur- 

 face without folds, uniformly and finely punctate. 



The generic relations of these teeth are somewhat obscure, 

 but they approach most nearly those described in the 4th volume 

 of the Geological Report of Illinois, p. 369, PI IV., fig. 3, with 

 the name Sandalodus c7-assus ; the teeth of that species are, 

 however, longer, narrower at the anterior extremit}' and less 

 symmetrically arched behind. Among a large number of teeth 

 of Sandalodus crassus recentl}' received from Mr. William Mc- 

 Adams, Alton, 111., are some which are quite complete, and these 

 show a prominent point extended from the straight side bevond 

 the crown surface, a feature which does not appear in the fig- 

 ure cited. Probably such a point or angle projected from the 

 posterior end of the teeth before us, so that the general outline 

 was less elliptical than that of the crown surface. 



Mr. Orestes St. John has transferred Sandalodus crassus to 

 his genus Orthopleurodus, perhaps with i^eason, though it is sep- 

 arated somewhat widely from 0. carbonarius of the Coal Meas- 

 ures. The teeth under consideration could not follow Sandalo- 

 dus crassus into Orthopleurodus, as the anterior extremity is 

 broader and rounder and neither side is straight. 



With the nearly complete tooth now figured is a fragment of 

 another which was apparently about the same size and shape and 

 is evidently the corresponding tootli from the other side of the 

 mouth. Taken by itself this fragment might readily be mis- 

 taken for the posterior extremit}^ of a tooth of average size of 

 Sandalodus crassus, but the anterior portion is wanting. If the 

 more complete tooth has sufl^ered no injury, its rounded extrem- 

 ity separates it widely from all species of Sandalodus and brings 

 it nearer in form to the tooth which I obtained from the Keokuk 

 group in central Kentucky and described in Vol. II. of the Pale- 

 ontology of Ohio, p. 38, and named Platyodus lineatus. Since 

 then Mr. St. John has described, in Vol. VII. of the Report of 

 the Geological Survey of Illinois, p. 82, a large though imperfect 

 tooth from the Kinderhook' group, which may have had some- 

 what the form of those now under consideration, and is, perhaps, 

 referable to the same genus. This tooth he has called Vaticino- 

 dus vetustus. Unfortunatel}' all the anterior portion of the tooth 

 is lacking, and therefore satisfactor}' comparisons cannot be made. 

 All these teeth have a general resemblance in their oblong or 

 elliptical outline and low arched crown to the tooth of Platyodus 

 referred to above, and j^et the linear punctation of that tooth in- 

 dicates differences that are probabl}' generic. 



With more material it may be necessar^^to give the teeth now 

 described a new generic name, but without such material it would 



