190 



The scales are thin ami cycloid, and, though largo, arc not reniarkaljly so 

 for tlic size of the fish. They are not readily preserved. 



Measurements of the cranium. 



M. 



Length from the augle of the opisthotic to the anterior extremity of the ethmoid 0. ;'0 



Length from the angle of the opisthotie to the front of the proiitic 0. 11 



Length from the postfrontal to the prefrontal across the orhit 0.11 



Length from the occipital condyle to the transverse process of the parasphenoid 0. 117 



Length i'roni the occipital condyle to the bottom of the parasphenoid emargination 0.0.").') 



Length of the parietal hone on the outer suture 0.07 



Width of the parietal boue at the middle 0. 014 



Width of the parietal bone to the edge of the pterotic 0.07 



Width of the frontal at the middle of the orbit 0.04 



Width of the parasphenoid at the middle orbit 0.03 



Length of tile inferior cpiadrate 0. 10 



Length of the condyle of the inferior quadrate 0.03 



Length of the symplectic 0.064 



This cranium is figured on Plate xxxix. 



The gape of the mouth of the Fortheus wolossus extended the whole 

 length of the cranium proper, and far beyond the orbits, since the maxillary 

 reaches to opposite the occipital condyle. The orbits were large. The lower 

 jaw was deep, and gave the countenance that bull -dog expression from which 

 it derives its name. The body was stout and moderately elongate. 



A comjjlete cranium of u Portlieus, probably the P. molossus, for which 

 I am indebted to my friend Professor Merrill, of Lincoln University, at 

 Topeka, Kans., furnishes several points of interest previously unknown. The 

 moiitli is nearly vertical, somewhat as in Osmeroides, while the vertex is sur- 

 mounted by an elevated crest. Hence, the superior and inferior facial out- 

 lines meet at a right angle at the muzzle. The eye is small, and there is a 

 suborbital chain of laminiform bones. The elevation of the skull is 16.75 

 inches, while the length is only 12.75 inches. Cut 8, page 184, represents 

 this specimen. 



PORTHEUS THAUMAS, Cope. 



SuuroccphaTua thaumas, Cope, Proceedings of the American Philosoiihical Society, 1870, November ; 

 Hayden's Survey of Wyoming, &c., 1871, p. 418. 



This large species rests on a specimen without cranium, originally pro- 

 cured by Prof. B. F. Mudge. The parts preserved are not distinguishable 

 from the corresponding ones in two individuals obtained by myself in West- 

 ern Kansas, which include the greater portions of tlie jaws and suspensorial 

 apparatus. These indicate larger animals than those of P. molossus, and 

 one of the most powerful of the physostomous fishes, rivaling in this respect 

 many of the saurians, which were its contemporaries. 



