462 CHA.RACTEKS OF PALEOZOIC FISHES COPE. 



From tiie Permiau bed of the southern ludiaii Territory. Collected 

 by W. T. Cummins. 



I have been principally guided in the determination of this form by 

 the monograph of the Platysomidie published by Dr. Traquair, in the 

 Transactions of the Royal Society of Edinburgh, vol. 29, p. 343. J)r. 

 Traquair there demonstrates clearly that the Platysomid:e belong to 

 the Lysopteri near to the Pahftoniscida^, and that they are not allied 

 to the DapediidoB. 



Platysomus lacovianus sp. nov. 



Radial formula : D. 28, C. 30, A. 25. Body deep, superior and in- 

 ferior outlines very convex, superior convexity posterior to the inferior. 

 Scales in nearly vertical series of few in a series, each scale with about 

 nine closely placed parallel ridges. These are parallel to the sides of 

 the scales in the lower and middle parts of the body, but on the superior 

 regions they are directed forwards as well as downwards, being oblique 

 to the long axis of the scale. The ventral border is furnished with a 

 single series of scales with a free acute extremity, forming a serrate 

 line. No such series is noticed on the dorsal outline. The head is 

 badly preserved ; the x^terotic and j)ost-frontal regions have a striate 

 sculpture like that of the scales. 



Measurements. 



Min. 



Length of spcciiueu '^7 



Greatest depth of specimen 22 



Length of base of dorsal fin 7 



This species is probably allied to the Platysomus circularis M. & W.* 

 In it the radial formula is given at D. 40, C. 30, A. 30. The scales are 

 also said to be smooth. This may be an appearance only, due to the 

 loss of the ganoine layer ; but if correctly stated the scales are very 

 difierent from those of the P. lacovianus. 



The typical and only specimen of the P. lacorianus is preserved in the 

 cabinet of Mr. SI. 1). Lacoe, of Pittston, Pennsylvania, to whom I am 

 indebted for the opportunity of examining it. It is in a concretion from 

 the Coal Measures of Mazon Creek, Illinois. 



# 



Report of the Geological Survey of Illinois, p. 317, PI. iv, Fiji. 2. 



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