lyo 



THE PERMO-CARBONIFEROUS RED BEDS OF 



but taken as a whole seem certainly to belong together. The largest specimen, 

 evidently from an adult form, resembles most remarkably the humerus of 

 Ophiacodon minis Marsh (fig. 31 A, Publication 181, Carnegie Institution of 

 Washington; fig. 5, plate 35, Amer. Perm. Vertebrates) . The differences noted 

 between this bone and the humerus of Ophiacodon are: In Ophiacodon the 

 distal and proximal ends are "relatively little divergent"; in this form they 

 are at right angles. The ectepicondylar process in Ophiacodon extends dorsally 

 at nearly a right angle; in this form it extends dorsally and outwards at an angle 

 of 45°. The radial condyle of Ophiacodon is nearly circular and looks largely 

 forward ; in this form it is smaller and looks more distally than forward. 



Table 4. — Proportional Measurements of Specimens. 



In the smaller specimens the ectepicondyle is less prominent and the 

 articular faces are less well formed and distinct, as would be expected. The 

 proximal articular face is continued out upon the deltoid process, but in the 

 larger bones this connection is broken by the connecting ridge becoming 

 thinner until the face upon it disappears. The entepicondylar foramen is 

 nearer the lower end. 



The second type of humerus is so radically different from any form as 

 yet discovered in the Texas beds that it is certainly new and may be called 

 Archeria rohinsoni. The whole bone (plate 23, figs. 7 and 8, fig. 44, a and b), 

 represented by one complete and two incomplete specimens (No. 3246) , is very 

 thin and broad, resembling in this character the form assigned to Cricotus, but 

 differs from it very largely in other particulars. The articular surface of the 

 proximal end is confined to the inner half of the extremity and has the obhque 

 position common to the Pelycosaurs. The deltoid process is well down on the 

 anterior side and has a large facet deeply sunk in the end of the process. The 

 outer edge of the bone is thin, terminating in a knife-edge ; it originates from 

 the back of the deltoid process and curves sharply backward at first; turning, 

 it runs straight down to the distal extremity, becoming slightly thicker at the 

 distal end. The inner edge runs slightly inward for its proximal one-third or 

 more and then bends sharply outward on the entepicondylar process at nearly 

 a right angle to its former course. This edge is thin, but not sharp, as is the 

 outer edge. The entepicondylar process is large, being approached in this 

 regard, so far as I know, only by Casea and the Diadectid reptiles. The entepi- 

 condylar foramen perforates the bone just at the point of junction of the 

 process with the shaft. The inner edge of the process has a very narrow face, 

 with evidence of the attachment of a cartilaginous extension. 



