348 PALAEONTOLOGY OF ILLINOIS. 



back and accurately opposite; ventral fins set about tbe mid- 

 dle of the body; scales rhomboidal, of nearly uniform size 

 except on the tail, smooth on surface and margins. 



This elegant little fish seems to be quite distinct from any heretofore found 

 in this country. It is much less in size than any species of the genus before 

 known, sometimes hardly exceeding an inch in length. The body is elongated 

 and narrow, bearing simple polished scales. The dorsal and ventral fins placed 

 so near the caudal as to almost reach it when collapsed, and are exactly oppo- 

 site. In this character it is unlike any other species known. 



It might be inferred that this was but the young of P. peltigerus, N., the most 

 common species in the Coal Measures of the Western States, but it wants the 

 row of large scales which cover the dorsal line of that species, and also differs 

 from it in the position of the fins and the smooth scales. In size it is about 

 equal to Eurylepis minutus, N., found in the cannel coals of Ohio, but is more 

 slender, has the fins differently placed, and wants the high side-scales of that 

 species. 



Formation and locality: Coal Measures; Mazon creek, G-rundy county, 111. 



GENUS AMBLYPTERUS. 

 AMBLYPTERUS MACROPTERUS ? Ag. 



A somewhat shattered nodule of clay ironstone obtained by Mr. S. S. Strong, 

 from the Coal Measures at Mazon creek ; contains an unmistakable impression 

 of a species of Amblypterus, the first that has been recognized in America. 

 From the mutilated condition of the specimen, it is impossible to decide with, 

 certainty whether it was or was not identical with either of the species found 

 in the Coal Measures of Europe, but it so closely approaches A. macropterus, 

 Ag., so abundant in the similar nodules of ironstone at Saarbruck, that we are 

 not justified in giving it a new name. Other specimens, which it is to be 

 hoped will be discovered in the locality that has furnished this, will doubtless 

 decide the question. In either case, this adds another to the list of genera 

 and species found in that wonderful deposit of Mazon creek, and affords addi- 

 tional evidence of the minute and exact parallelism between the Coal Meas- 

 ures of Europe and America. While we may leave the correspondence between 

 other parts of the geological column on the two sides of the Atlantic open to 

 further proof as to whether they be cases of homotaxis or synchronism, we 

 must insist that here, at least, the phenomena were coincident in time, and are 

 due to cosrnical and not to local causes. 



