MORPHOLOGICAL REVISION 



91 



Diplocaulus magnicornis Cope. 



The description of the genus given above is drawn from both of the well- 

 known species. D. magnicornis seems to have been somewhat larger than 

 D. limbatus and to be very clearly distinguished by the form of the skull and 

 the relations of the bones. The following measurements are drawn from 

 several specimens: 



No. 4472 Am. Mus. : mm No. 652 Univ. of Chicago — Continued: mm 



Breadth across horns 400 Length of second vertebra 11 



Length on mid-line 13 1 Expanse of transverse processes. . . 46 



Length three middorsals 72 Length of third vertebra 13 



No. 4539 Am. Mus.: Expanse 48 



Breadth across clavicles and inter- Length of fourth vertebra 14 



clavicle.. 129 Expanse 50 



Anteroposterior length of inter- Length of fifth vertebra 17 



clavicle 100 Expanse 48 



No. 652 Univ. of Chicago: Length of sixth vertebra 20 



Breadth across horns 348 Expanse 48 



Length on mid-line 120 Length of seventh vertebra 21 



Length of atlas 20 Expanse 46 



Greatest expanse of same 32 



Diplocaulus limbatus Cope. 



The distinction between this species and magnicornis, suggested by 

 Cope and based on the character of the quadratojugal and the otic notch, 

 does not seem to be determinative; the conditions described by him are due 

 to the pressure and are not correlated with the other differences. Measure- 

 ments are given in the original description of the species. 



Genus ERYOPS Cope (p. 24). (Plates 4-10.) 



Characteristic specimens: Nos. 4673, 4183, 4180, 4893 Am. Mus. Nat. 

 Hist. Cope Coll. and No. 117 University of Chicago. 



The genus Eryops, though one of the most abundant forms in the Texas 

 beds, has but one well-known species, E. megacephalus; other species have 

 been named, but are so insufficiently known as to make their determination 

 uncertain. Several other genera and species have been named from verte- 

 brae and parts of skeletons which have later been shown to be synonyms 

 of Eryops; such are Rhachitomous valens Cope and Epicordylus erythroliticus 

 Cope. Parioxys ferricolus Cope was regarded by Cope himself as a young 

 Eryops, but it seems to have certain distinctive characters and is considered 

 in this paper as a distinct genus and species. 



The following description drawn from several specimens applies entirely 

 to Eryops megacephalus. Aside from the descriptions by Cope, two papers 

 by Broili (3) and Branson (2) have been freely drawn on. 



The skull is not disproportionately large, as is so common in the Paleo- 

 zoic and Mesozoic Amphibia. The surface of both skull and jaws is covered 

 by a very rough sculpture of deep pits, which become larger on the posterior 

 portion of both skull and jaws. The orbits are located in the posterior half 

 of the skull, and look upward and but slightly outward. The upper edge 

 is marked off from the depressed interorbital region by slightly elevated 

 ridges. The articular region extends well back of the occipital condyles, 

 and there are well-developed otic notches. The bones of the skull are rather 

 thin, especially in the preorbital region, so that this part is frequently broken 

 and missing. The nostrils are set well back from the anterior end of the 



