VERTEBRATES. 81 



species noticed respectively from the St. Louis and Chester forma- 

 tions, as will be remarked further on. The earliest representative 

 occurs in the upper horizon of the Kinderhook formation, the Upper 

 Burlington, St. Louis and Chester each contributing representative 

 forms, while a single form from the Upper Coal Measures, and one 

 from the Lower Coal Measures, are with doubt here referred. The 

 Kinderhook and Upper Burlington afford the typical representatives, 

 being represented by examples which it is difficult to believe ever 

 possessed the distinctive characters essentially attributed to Deltop- 

 tijcldus. We owe to the kindness of Lord Enniskillen opportunity to 

 compare, from drawings, a magnificent tooth derived from the Car- 

 boniferous limestone of Oreton, in Shropshire, England, and belong- 

 ing to the museum at Florence Court, Ireland. The latter tooth 

 shows a large example, above four inches in its greatest diameter, 

 and of proportionate dimensions, of the maxillary posterior form. 

 So far as it is possible to judge from the drawings, it possesses pre- 

 cisely the coronal contour characteristic of the teeth of the corres- 

 ponding form noticed in the following pages. The resemblances in 

 common between the Shropshire and the Kinderhook teeth are 

 especially pronounced, neither the one nor the other would be mis- 

 taken for a typical Deltoptychius. In both examples the posterior 

 prominence is obscurely defined from the plain anterior region, 

 which shows not a trace of secondary lobe. The genus may also 

 include the tooth described by Dr. L. de Koninck 1 under the name 

 Streblodus tenerrimus, from the Lower Carboniferous deposits of Tour- 

 nay, Belgium. 



Again, if the evidence be fairly admissible, the forms here especi- 

 ally referred to, offer some most interesting suggestions bearing on 

 the derivation of allied and coexisting generic forms. That referred 

 to under the name Vaticinodus vetustus, from the Kinderhook, rep- 

 resents the earliest species not only of this particular group, but 

 also of typical Cochlwdonts. Passing up into the Upper Burlington, 

 next is met with an apparently congeneric form V. discrepans. Dur- 

 ing the latter epoch Chitonodus, the immediate precursor of Cochlio- 

 dus, was introduced, and also Deltoptychius and Stenopterodus. The 

 latter is plainly a somewhat more pronounced differentiation, while 

 Deltoptychius holds an intermediate place between the primal groups 

 and Stenopterodus. 



(NOTE.) * Faune calcaire Carbonifere do la Belgique, II, p. 55, P. VI, f. 13. 



