36 PALEONTOLOGY OF OHIO. 



possible, therefore, that we have in this fish an ally of MacropetaUchtliys^ 

 and thus, perhaps, a Chondrostean in which, as in the sturgeon, the sides 

 and lower portions of the head were protected simply by a leathery integ- 

 ument. Future discoveries will doubtless make more plain what is now 

 so obscure in the structure of this fish. 



AsTEROSTEUfi STENOCEPHALUS (ll. Sp.). 



Plate LI v., Fig. 1. 



Head 8 inches or more in length, by 2^ inches in width, except 

 at the occiput, where it suddenly widens and becomes 4 or 5 inches 

 broad. It terminates posteriorly in two excavated arches, of which 

 the surface is roughened, apparently for muscular attachment. Pro- 

 jecting behind and below these arches are two bony condyloid prom- 

 inences an inch or more in length. The upper surface of the cranium is 

 somewhat irregularly covered with stellate tubercles which vaiy in size 

 from one-eighth to one-twentieth of an inch in diameter. The sides of 

 the cranium are somewhat beveled and roughened, and are traversed by 

 an irregular line of relatively large tubercles. jSTear the anterior end the 

 liead seems to be suddenly narrowed, and just at this point it bears two 

 deeply impressed, elliptical, nasal (?) orifices, placed side by side, somewhat 

 divergent forward, and having a length of 5 lines and a breadth of 2 

 lines. The dentition is entirely unknown, as also the covering of the 

 body. 



Formation and localiy : Corniferous limestone, Sandusky and Delaware, Oliio. 



OEPHALASPIDJE (?) 

 Genus ACANTHASPIS (iiov. gen.). 



This name is used to designate certain cranial bones of what seems to 

 have been a Cephalaspid, found in the Corniferous limestone of Ohio. 

 Considerable variety is noticeable in the shape of these plates, and it is ap- 

 jjarent that they formed parts of a tessellated cranium. They are generally 

 somewhat oblong in form, the greater part of the plate being quadrangu- 

 lar, while one of the margins is oblique and prolonged into an acute 

 point, and to this margin is spliced a carinated, toothed spine, sometimes 

 four or five inches in length. These spines bear considerable resem- 

 blance to the dorsal spines of some extinct sharks. They might, indeed, 

 under some circumstances, be accepted as the spines of Gtenacomthus, 



