244 PALEONTOLOGY OF ILLINOIS. 



ACONDYLACANTHUS? MtJDGIANUS, St. J. and W. 

 PL XXIV. Fig. 3. 



A fragment from the Upper Coal Measures of Kansas represent, 

 ing a medium-size ichthyodorulite is provisionally referred to the 

 above genus. The specimen preserves a length of about 7 centi- 

 metres, apparently of the middle or lower portion of the spine, of 

 which the entire anterior border is broken away, revealing the deeply 

 excavated posterior face or the pulp cavity, bordered by a strip of 

 the thick lateral walls near the postero-lateral angles. The trans- 

 verse section of the spine is subtriangular, moderately arched along 

 the anterior edge, lateral surfaces evidently gently convex trans- 

 versely, and, so far as revealed by the remaining walls, ornamented 

 by simple, angularly rounded longitudinal costse, separated by deep, 

 narrow intercostal grooves ; the costse enveloped in the smooth 

 enamel layer throughout. Beyond this the superficial features are 

 not disclosed, and so little remains that the moderately rapid taper- 

 ing of the spine is hardly more than an inference. 



While the generic relations of the specimen above referred to are 

 by no means satisfactorily authenticated by the meagre characters 

 that remain, its specific distinctness from any form occurring in 

 the Coal Measures as yet discovered is unmistakable. The specific 

 designation is given in honor of the late Professor Benjamin F. 

 Mudge, the distinguished educationist and director of the first State 

 geological survey of Kansas. 



Geological position and locality: Upper Coal Measures ; Eock Creek, 

 Pottawattomie county, Kansas. 



ACONDYLACANTHUS? XIPHIAS, St. J. and W. 



PI. XXVI, Fig. 1. 



The unique example here referred to presents the larger portion 

 of a large dorsal spine, probably between 20 and 23 centimetres in 

 length, of which perhaps 5 centimetres of the distal extremity are 

 broken short off, while the inserted portion shows evidences of cur- 

 tailment in the rounded anterior margin. Besides, the surface of 

 the exposed portion of the spine is evidently much worn, the costs 

 for the most part destitute of enamel, disclosing the irregularly 

 pitted bony structure in common with that of the intercostal grooves, 

 so that it is impossible to arrive at a satisfactory conclusion in re- 

 gard to the character of the superficial ornamentation, upon which 



