MORPHOLOGICAL REVISION OF THE SUBORDER. 8l 



remnants of the first and second digits show that the foot was fairly long with well- 

 developed digits and claws. 



Dermal ossifications : Two or three fragments of dermal ossification remain to 

 show that the lower surface of the body was protected by slender, elongate rods of 

 bone. The only fragments preserved cling to the lower surface of the vertebral col- 

 umn and the lower surface of the humerus. 



Measureme7its. 



mm, mm. 



Total length of the skull in the median line 145 Width of nares 5 



Width of skull over the foramen magnum 45 Distance from posterior border of nares to an- 



between orbits 20 terior border of the orbit 77 



between external nares 10 Height of the skull over the foramen magnum, 



Antero-posterior diameter of orbits 26 measured with the lower jaw 47 



Width of orbits 29 Length of tibia 64 



Antero-posterior diameter of nares 7 fibula 67 



This animal veiy closel}^ resembles Poliosaunis and was evidently 

 closely related to it both in structure and habits. 



Genus THEROPLEnRA Cope (seep. 22). 



The discussion of the genus is largely contained in that of the iirst 

 species below. The animal was undoubtedly closely similar in form of body 

 to Varanosaums and probably had the same habits. The form of both was 

 elongate and low ; the short legs permitted the belly to drag on the ground 

 and the tail was long and slender. The chief difiference in external appear- 

 ance was that the head of Varanosaurus was narrow and elongate, while that 

 of Theropleura, though long, was wider and flattened. 



Theropleura retroversa Cope (see p. 25, plates 3-13). 



TherofUura triangulata Cope, p. 25. Clefisydrofs leftoce;phaius Cope, p. 26. Diopeus leftoce- 

 fhalus Cope, p. 26. 



Characteristic specimens: No. 4155 American Museum, the type (Trans. Am. 

 Phil. Soc, vol. XVII, plate 2, fig. 8j. No. 4026 Am. Mus. Nat. Hist., Cope, coll., 

 femora. No. 1013 University of Chicago, fragments of a skull. No. 1014 University 

 of Chicago, left maxillary. 



The skull is unfortunately poorly preserved ; the bones are clean and in good 

 condition, but many important ones are missing. Cope first recognized the double- 

 arched character of the skull in 1892 (78), but described only the temporal region (see 

 systematic revision, p. 26). In 1903 the author published a redescription of the skull, 

 showing the general form and proportions ; later studies have made it necessary to 

 alter somewhat the interpretation in the region of the temporal arches. 



The skull was elongate and low, with a broad, flat top, more like the living 

 Varaniis than Dimetrodon. The maxillary extended upward somewhat, but the 

 facial region was not elevated ; the frontals are as broad as the maxillar>- is high ; in 

 Dimetrodon the frontals are very narrow, not over a fourth or fifth as wide as the 

 maxillary is high. 



T\\Q premaxillary is similar to Dimetrodon ; there is a long median process pro- 

 jecting backward to meet the nasals in the median line. The bones of the two sides 

 meet by a broad and strong sutural surface. There are five teeth ; the first two were 

 abruptly larger, the four posterior ones are small. 



