lateral ridges of T. triangulata are situated low down on the centra. The 

 diapophyses supporting the tubercular articulation are frequently elongate. 

 The scapular and pelvic bones are of the usual type. The humeri be- 

 long to form second of my Pal. Bull. No. 29. Thej r have rather slender 

 shafts, and much expanded extremities. The proximal articular surface is 

 Avell denned. The supracondylar foramen and other points are as in the 

 Pelycosauria generally. There were probably distal condyles, but this is 

 not absolutely certain. 



Measurements. M. 



Length of mandibular series of teeth (nearly complete), 



on block 110 



Length of crown of mandibular tooth 008 



Anteroposterior diameter of mandibular tooth 004 



Diameters of articular extremities of a ver- ( vertical . . . .021 



tebra on the same block ( transverse. .020 



Length of another centrum on same block 020 



( ( f 1 \i larger " ' ,065 

 Diameters of humerus (separate) -< ° ieac ( smaller. .013 



(of shaft 017 



The above description represents the parts which belong either certainly 

 or very probably to one individual. Bones of a second and larger animal are 

 mingled with these. The species to which they belong is uncertain, but 

 they resemble very much those of the Theropleura obtusidens, and may be- 

 long to a larger individual of that species. A femur has the form already 

 described under the head of Clepsy drops natalis. (Paleontological Bulletin, 

 No. 29, p. 510.) Some phalanges belonging no doubt to one or the other of 

 the two animals, are like those I have already ascribed to Clepsydrops. 

 They are depressed, and are expanded at the articular extremities. The 

 distal extremities expand the most abruptly, and their convex trochlear face 

 is without groove or keel, and is more extended on the inferior than the 

 superior surface. 



DIMETRODON Cope. 



Proceedings American Philosophical Society, 1878, p. 512. 



The accession of a considerable amount of material representing this 

 genus enables me to add important points to our knowledge of its osteology. 

 The most noteworthy additions include the greater part of the skeletons 

 of two individuals of D. incisivus ; and vertebras attached to the pelvis 

 and femora of D. gigas. There are also vertebras of several individuals of 

 D. cruciger, and various parts of the skull of a species distinct from the D. 

 incisivus. 



In both specimens of D. incisivus, portions of the palatopterygoid arch 

 are attached to the maxillary bone. One of these elements is an oval plate 

 with a thickening of its inferior side, so as to bevel the long border farthest 

 from the maxillary bone. The surface thus produced is thickly studded 

 with small conical teeth irregularly disposed. 



A second tooth-bearing element of the palate is adjacent to the last. It 



