VEETEBEATES. 337 



appearance. In transverse diameter the teeth range from less than .15 

 to 1.05 inch. 



The varied dentition indicated by these teeth renders this one of the 

 most interesting of the numerous Orodont species occurring in our 

 Carboniferous rocks. In the mature or larger teeth, the coronal lobes 

 approach more nearly the condition ascribed to Orodus, while in the 

 small teeth, with the exception of the acutely produced median cone, 

 the superficial characters even more resemble certain forms of Helodus, 

 or the small teeth of certain Psephodi. In their diversity they recall 

 the dentition of Cestracion — the small, acutely conical teeth correspond- 

 ing to the prehensile teeth in the anterior part of the mouth, while the 

 posterior teeth become less and less prominent and acutely apiculate, 

 until reaching the low, obtusely conical or depressed teeth which com- 

 posed the rows in the posterior portion of the jaws. 



The collections from the Keokuk limestone also afford a few examples 

 of teeth, which are indistinguishable from the Burlington specimens, 

 except that they are apparently more coarsely punctate. Our series of 

 these specimens is so small, however, as not to exhibit their distinguish- 

 ing characteristics, if such they possess, by which they may be recog- 

 nized from the form described above, though they may be indicated 

 provisionally by the name L. grossvpunctatus. The latter specimens 

 occur in the Keokuk fish-bed horizon at Keokuk, Iowa, and Warsaw, 

 Illinois. 



Position and locality : K"ot uncommon in the fish-bed of the Upper 

 Burlington limestone; Louisa and DesMoines counties, Iowa; Hender- 

 son and Warren counties, Illinois. 



Gextjs DESMIOD US, St. J. and W. 



Teeth occurring in series or rows extending from the inner to the 

 outer border of the jaws. Individually the teeth are of small size, 

 robust. Crown laterally elongated, more or less strongly arched verti- 

 cally, culminating in a strong, subconical, median prominence, which is 

 strongly buttressed in the outer or concave face by an angular vertical 

 ridge, laterally flanked by the obtusely angular crests, which are more 

 or less strongly denticulated, inner face more or less regularly arched 

 in both directions, anterior face gently concave or plane vertically, more 

 or less strongly produced along the basal line in the median region, 

 extremities rouuded, basal borders inbeveled and occupied by a simple, 

 wide coronal fold, which slightly overlaps the produced borders of the 

 superior coronal region ; surface polished, smooth or delicately marked 

 along the crest by sharp threadlike costa3, and in the edge of the coro- 



