MORPHOLOGICAL REVISION OF THE SUBORDER. II3 



area of squamous suture which would just accommodate such a degenerate element as 

 is indicated by the specimen of Clepsydrops. 



The clavicles are wide and thin anteriorly and taper to a point at the distal end ; 

 near the middle of the lower edge there is a slight rugose prominence. It is not 

 probable that the clavicles met on the lower side of the interclavicle, but they covered 

 the anterior end in large measure. 



The mterclavtc/e is very elongate. A separate specimen, No. 105 1 University of 

 Chicago, is nearly perfect; it shows that the anterior end was thickened and enlarged; 

 the lower surface is sharply rounded, so that it is almost hemispherical with the con- 

 vexity downward. The lower surface is quite rough with radial sculpture ; the upper, 

 inner, face is smooth. The edges of the anterior end are not complete, but enough 

 remains to show that there was no articular face for the clavicles and that they over- 

 lapped the anterior end nearly to the middle line. The posterior prolongation is 

 nearly flat, but the midline is thicker than the edges. The posterior end is marked 

 with rugose ridges. The total length of the specimen is 275 mm. (plate 15, fig. i). 



The fore limb is described from specimen No. i University of Chicago, and the 

 fore foot from No. 1003 University of Chicago, both D. incisivus. 



The humerus is without prominent condyles at the proximal end. The articular 

 face is a narrow, concave area winding obliquely across the laterally expanded proxi- 

 mal end from behind, forward, and inward. The radial crest is very prominent ; it 

 starts from the proximal extremity of the bone and grows to a prominent ridge which 

 stands at almost a right angle to the rest of the bone. Culminating in a strong tuber- 

 osity it extends downward, crossing the shaft obliquely and disappearing on the inner 

 edge of the entepicondyle and helping to complete the entepicondylar foramen (plate 

 14, fig. 3). The distal end is expanded at nearly a right angle to the proximal end. 

 The ulnar articular surface is rather saddle-shaped, and somewhat diagonally placed 

 on the outer extremity of the distal end. There is no anconeal pit on the posterior 

 face of the bone. The radial condyle is largely on the anterior face ; it is a hemispheri- 

 cal prominence. The entepicondylar foramen is situated near the upper part of the 

 entepicondyle and is oval in outline. On the ectepicondyle a prominent, sharp pro- 

 cess defines an ectepicondylar notch. 



The ulna is a slender bone, somewhat longer than the humerus, with a flattened 

 shaft. The shaft becomes gradually smaller toward the distal end and then expands 

 slightly again. The proximal end is excavated on its anterior face by a deep fossa 

 looking, in the natural position of the bone, upwards as well as forwards. This cavity 

 is divided by a low ridge into two facets, the larger looking forwards, and the smaller 

 and external one looking slightly outwards. The proximal extremity extends above 

 the articular face and forms the olecranon process. The outer side of the process has 

 a convex, rugose surface. The distal end is divided into two distinct articular faces 

 (plate 14, figs. 6 and 7). 



The radius is curved and rather shorter than the ulna. The shaft is lenticular 

 in section with the edges becoming sharp and prominent toward the distal end. The 

 proximal end is expanded and the articular face for the humerus is deeply concave and 

 somewhat crescentic in outline. The distal end is less expanded and the single articu- 

 lar face is a shallow pit, oblong in outline. 



"^he^ fore foot (No. 1003 University of Chicago): The length of the humerus with 

 which this foot was found is 210 mm., while that of No. i is 181 mm., so that it belongs 

 to a slightly larger animal. The carpus as preserved consists of eleven elements. The 



