SYSTEMATIC REVISION 



23 



well-defined sutures led him to the belief that it was the adult of another 

 species. Skull very flat and small. Length on the middle line of one, 2.6 

 cm.; of another 1.9 cm. Sculpture as in the larger forms but finer, so that 

 the pits of the larger skull are here small points. Centers of ossification can 

 be made out in the individual bones, but there are no traces of slime canals 

 or of a sclerotic ring in the eye. Orbits and nares in relatively the same 

 position as in Diplocanlus. Supraoccipital relatively large and broad, meet- 

 ing the epiotic (tabulare) laterally. Large parietal not clearly separated 

 from the frontal. Frontals apparently united in a single bone. Quadrato- 

 jugal a slender element forming the side of the posterior part of the skull, 

 which is continued backward into well-developed horns. Space between 

 the quadratojugal and the parietal filled by a single element which, in all 

 probability, must be considered as the supratemporal. The sutures of the 

 anterior part of the skull can not be made out. The lower jaw with an incon- 

 spicuous sculpture, longer than in other species of the genus, reaching to a 

 length equal to one-half the length of the skull. The slender teeth conical, 

 smooth, and of equal size. Four vertebrae, beginning with the atlas, are 

 visible from the upper side; they are similar to those of Diplocaulus except 

 that the atlas is more slender. Interclavicle elongate rhomboidal, with the 

 sculpture radiating from the center of ossification, which lies about in the 

 middle of the plate. The clavicle has a leaf-like outline with the center of 

 ossification near the outer border. 



Fig. 3. — Diplocaulus (?) pusillus. X I after Broili. 



A, upper view; B, upper view of a second specimen; C, 

 lateral view of a third specimen. 



'', frontal; p, parietal; so, supraoccipital plate; qj, quad- 

 ratojugal ; St, prosquamosal ; m, mandible; mx, 

 maxillary. 



Williston, in the paper cited, regards it as very doubtful whether this 

 form belongs to the genus Diplocaulus. 



Revised descriptio7i: So far as our knowledge now goes, the original descrip- 

 tion seems adequate for this uncertain form. A specimen of this animal, 

 No. 4523 Am. Mus., strongly suggests relationship to Trimerorhachis. 



Suborder TEMNOSPONDYLl Zittel. 



A. RHACHITOMUS division. 



Family ERYOPID^ Cope. 



Cope, Am. Nat., vol. xvi, 1882, p. 334. Proc. Am. Phil. Soc, vol. xx, 1882, pp. 

 460-461. Syllabus of Lectures, 1891, p. 29. Syllabus of Lectures, 1898, p. 46. 



Original description: In the first paper Cope suggested the recognition 

 of a new suborder, the Rhachitomi, which he divided into two families: 



"Occipital condyle concave, undivided Trimerorhachidtz 



Occipital condyle divided into two lateral condyles Eryopida" 



Revised description of the family: 



1. Small to large. Reaching from 2 to 2.5 meters in length, 



2. Occipital condyles distinct. 



3. Otic notch small. 



4. Parasphenoid large joining a basioccipital posteriorly. 



5. A single sacral rib. 



6. No dermal armor on back. 



