VERTEBRATES. 249 



the pulp cavity, the carinate matrix of which would indicate, per- 

 haps, a rather prominent median angularity in the contour of the 

 posterior face of the spine. Although we have no evidence of the 

 denticles arming the postero-lateral angles, and even the wide fur- 

 row immediately adjacent the anterior keel is destitute of the char- 

 acteristic tubercles, nevertheless the character of the striato-punctate 

 intercostal furrows, as also the general facies of the specimen, leave 

 little room to doubt its generic identity with Asteroptychius. It is at 

 the same time readily distinguished specifically by its extremely 

 compressed, slender form, in which respects it presents marked con- 

 trast with the congeneric form Asteroptychius bellulus, St. J. and W., 

 from the Lower Coal Measures. 



Geological position and locality. Upper Coal Measures ; calcareous 

 shales overlying the coal at Topeka, Kansas. 



GENUS GLYMMATACAKTHUS, St. J. and w! 

 GLYMHATACANTHUS BUDIS, St. J. and W. 



PI. XXV. Fig. 1. 



Dorsal spine large, slightly curved and somewhat rapidly tapering. 

 Transverse section wedge-shaped, lateral surfaces slightly convex, 

 meeting in the sharply rounded anterior edge, posterior face not 

 shown. The lateral surfaces diverge at an angle of 30 to 35, oc- 

 cupied by widish, rounded costse, bifurcating below, separated by 

 sharp impressed lines, and bearing along their crests irregularly- 

 shaped, compressed, conical, closely arranged tubercles, which pro- 

 duce an exceedingly rough, rudely sculptured effect. The anterior 

 angle of the spine is flanked by a pair of costse, which support 

 approximately opposite tubercles. The tuberculation more or less 

 distinctly ranged in slightly oblique rows, ascending from the pos- 

 tero-lateral angle to the anterior border, and rudely sculptured by 

 radiating carinse. Pulp cavity large, apparently confined within the 

 posterior half of the spine, lateral walls thick. 



The unique example described above represents a fragment from 

 the middle of a large spine, both extremities and the posterior face 

 being broken away. The superficial costation and tuberculation, as 

 also the general form of the spine, accord well with the distinctive 

 characteristics of Glymmatacanthus. The specimen further shows the 



