VERTEBRATES. 273 



very produced laterally, deeply excavated inferiorly, deeply arched 

 inward between the quite prominent anteroinferior angles, and broadly 

 rounded into the more or less sharply rounded lateral extremities, 

 the antero median ridge moderately prominent. The median cone 

 does not differ essentially from tbat of G. politus, being erect, gradually 

 tapering, compressed in front and strongly rounded posteriorly, and 

 ornamented with numerous closely arranged striae ; the lateral denti- 

 cles, however, present the somewhat anomalous feature of possessing 

 in one extremity a third relatively strong cone exterior to the larger 

 lateral denticle, and which in lateral divergence and recurvation cor- 

 responds to the exterior denticle in the opposite extremity ; the lateral 

 cones are nearly circular in section, but ornamented in the same 

 manner as observed in the great cone. The hight of the specimen 

 particularly described above, and which represents about the largest 

 size attained by the other teeth, is about .40 inch, lateral diameter of 

 base .42 inch. 



It is possible that the tooth noticed above may prove to be distinct 

 from those with which it is associated; but we are inclined to regard it 

 as an abnormally developed tooth, or perhaps it represents a peculiarity 

 in the teeth from a particular part of the jaws. 



Mr. Van Hoene has also obtained from the Warsaw beds a very simi- 

 lar form of teeth ; but in the imperfect state of preservation which 

 without exception prevails in the few specimens thus far known from 

 that horizon, it is cptite impossible to more than recognize their general 

 resemblance to the section of the genus represented by the above men- 

 tioned forms. 



Position and locality : Upper beds of the St. Louis limestone; Alton, 

 Illinois ; St. Louis, Missouri. 



Cladodlts Van Hoenei, St, J. and W. 



PI. 4, Fig. 5. 



Teeth of large size, robust. Base irregularly elliptical, massive, 

 moderately arched, inferior surface deeply excavated, beveled belt 

 narrow, posterior margin thick, angularly rounded, extremities strongly 

 produced and sharply rounded, anterior border deep, produced, sinuose, 

 anterior basal angles prominent, and occupied by obtuse protuberances, 

 gently rounded into the extremities, and separated by a rather wide 

 depression, which extends up into the median cone, postero-superior 

 surface occupied by a strong lateral prominence in extent equal. to half 

 the diameter of the base, and abruptly defined behind, surface coarsely 

 roughened. Crown distinctly constricted at base in front, obscurely 

 defined behind, median cone very robust, rapidly tapering to an acute 



