540 C. R. EASTMAN 



developed, the pectorals unusually long, and anal much extended ; fulcra 

 minute. Scales relatively small, obliquely striated ; dorsal ridge-scales 

 enlarged. 



Only one individual is at present known of this interesting 

 little form, which is shown in Fig. 4. The head is poorly pre- 

 served, and the distal extremities of nearly all the fins are either 

 broken away or obscured by matrix. Nevertheless, sufficient 

 characters remain for the recognition of this as a distinct spe- 

 cies of Elonichthys, its chief peculiarity consisting in the remark- 

 able development of all the fins. The pectorals are fully one- 

 fourth the total length, and the anal has a more extended base- 

 line than in any other species of the genus. The dorsal appears 

 to have been high and acuminate, but is largely concealed by 

 matrix. The caudal is also unfavorably exposed, and flexed out 

 parallel with the main axis ; but it is plain that the upper lobe 

 was much prolonged, and covered with very large, striated ridge- 

 scales. The dorsal-fin rays appear to have been widely jointed ; 

 the articulations of the other fins are not clearly recognizable. 

 The dermal rays of the anal and lower lobe of the caudal are 

 directly supported by the large haemal spines, which are firmly 

 united with their arches. The squamation is nowhere well pre- 

 served, but is best indicated in the anterior part of the trunk. 

 The cranial structure does not admit of particular description. 

 Appearances suggest that the specimen here described is an 

 immature individual, differing however, from other known 

 species. 



LIST OF CARBONIFEROUS VERTEBRATES OCCURRING AT MAZON 



CREEK, ILLINOIS. 



ELASMOBRANCHII. 



1. Pleuracanthus {Diplodus) compressus Newb. (Occurs also in Ohio and 

 Indiana.) 



2. Pleuracanthus {Diplodus) latus Newb. (Occurs also in Ohio and 

 Indiana.) 



3. Pleuracanthus {Diplodus) lucasi Hay. 



4. Acanthodes beecheri Eastm. 



5. Acanthodes marshi Eastm. 



6. Campodus scitulus (St. J. and W.). 



