PERMO-CARBONIFEROUS VERTEBRATES FROM NEW MEXICO. 



27 



The femur is very similar to that of D. phaseoUnus, but rather more slender. 

 The head is convex dorsally, but with a deep trochanteric cavity on the ventral 

 face. The articular face is crescentic, confined to the end of the bone and somewhat 

 wider at the inner end. On the outer side of the proximal end is a strong process 

 inclined inward, on the bone of the right side, but this is probably due to crushing 

 and the process normally stood directly out from the body of the bone as in Dia- 

 dectes. The most prominent part of this process is just above the middle of the 

 shaft, and a short ridge extends downward to the middle of the ventral face of the 

 shaft ; this ridge can be traced as a low prominence obliquely across the face of the 

 shaft to the outer angle of the lower end. The shaft is proportionately longer than 

 in D. phaseoUnus, and oval in section, but the outline is marked by the prominence 

 just described and the narrower radial border. The lower end has the form com- 

 mon in the pelycosaurs and cotylosaurs; on the inner side is a semicircular face 

 for the tibia and on the outer a more elongate face (antero-posteriorly) for the 



Fig. 15. — Diasparacius zenos Case, X J4. A, upper surface of right tibia; 

 B , anterior view of right tibia ; C, inner view of right tibia ; D, inner view 

 of right fibula. 



fibula. The face for the tibia is semicircular in outline and is inclined downward 

 and backward; it is nearly cut off from the fibular face by deep grooves on both 

 the anterior and posterior sides of the bone. Just above the fibular face is a deep 

 pit on the outer side. 



In a specimen of D. phaseoUnus, No. 4684 American Museum, the articular 

 faces of the distal end of the femur are concave with raised edges, indicating the 

 presence of a considerable mass of cartilage; this condition, however, seems to be 

 peculiar to the particular specimen, and as it occurs on many of the articular sur- 

 faces may be due to exceptional conditions of fossilization or to the age of the 

 animal — especially as a similar condition does not occur in other specimens identi- 

 fied as belonging to the same species. In Diasparacius the articular faces are well 

 rounded and better formed, resembling the condition found in the Pelycosaurs 

 and indicating a more perfect joint. Compared with the femur associated with 

 the type skull of Chilonyx, the femur of Diasparacius is less rugose, shorter, and the 

 fibular face does not descend so far below the rest of the distal end of the bone. 

 The suggestions of similarity between Chilonyx and Diasparacius indicated by the 

 position of the quadrates is not borne out by the femora. 



The iibia is short and heavy, but this is not carried to the extreme seen in 

 Diadectes or Diadectoides. The proximal face is crescentic, due to the deep incision 



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