VERTEBRATES. 149 



So far as relates to the present unique example, little doubt can 

 arise as to its specifically distinct character ; but as regards the forms 

 with which it was specifically associated, the meagerness of the ma- 

 terial hardly furnishes a clue as to their identity. Thus far, the 

 Warsaw limestone has afforded only a few fragmentary remains of 

 Deltodus, some of which certainly are very intimately related to the 

 Keokuk species D. occidentalis (maxillary and mandibular posterior 

 forms) ; but the imperfect state of preservation of these specimens 

 offers nothing definite bearing on their specific identity, as noticed 

 in another place. We are satisfied that the species of Deltodus are, 

 in some instances at least, extremely intimately related to one 

 another, although distinguishable by well-defined peculiarities, as 

 exhibited by ordinarily well-preserved examples. However, amongst 

 the mass of material like that including D. occidentalis and D. un- 

 dulatus, of the Keokuk limestone it is impossible to recognize the 

 specific identity of the fragmentary individuals, and the same state 

 of things undoubtedly obtains in respect to allied representative 

 species. 



Messrs. NEWBEKKY and WOKTHEN have described (111. Geol. Surv. IV, 

 p. 367, PI. IV, f. 8) a maxillary terminal form under the name Del- 

 todus Littoni, reported from the Carboniferous limestone of Boone 

 county, Missouri. It is uncertain whether the latter, which is rep- 

 resented by an unique example, was derived from the Warsaw or 

 from the St. Louis formation, both of these formations, as also the 

 Keokuk, etc., occurring in the region indicated; however, the ap- 

 pearance of the limestone matrix does not suggest the latter horizon, 

 and it is supposed the specimen belongs to either the Warsaw or 

 the St. Louis. We owe to the courtesy of Dr. LITTON, of St. Louis, 

 the privilege of examining the type specimen. It is a large, much- 

 worn tooth, neither border of which is sufficiently complete to per- 

 mit of detail comparison with allied species. The relative great 

 breadth and regular convexity of the coronal ridge and apparently 

 narrow posterior alation, offer marked contrast to the prevalent 

 Keokuk species D. occidentalis, bearing a greater resemblance to D. 

 undulatus, especially, compared with worn examples of the latter 

 species, in which the transverse undulations are more or less ob- 

 scured, or obsolete. It is possible the narrow median tooth de- 

 scribed above may be specifically identical with the latter form, in 

 which event, of course, the name by which it is here designated 

 will have to give way to the prior term bestowed by Messrs. NEW- 

 BERRY and WORTHEN. 



