720 E. C. CASE 



Footbones. — There is a large series of footbones, the position of most of 

 which it is impossible to determine. They are all well formed, with good 

 articular surfaces, showing that the carpus and tarsus was fairly strong and 

 well knit. Some of the more common bones of indefinite position are shown 

 in Plate V, Figs. 18, a and b ; 19, a and b ; 20, a and b. [No. 6.559.] 



Astragali. — There seem to be two forms of astragalus. The first is much 

 the more slender and smaller. There are two distinct facets for articulation 

 with the calcaneum ; the upper of these is the largest and is separated from 

 the lower by a notch which, in combination with a similar notch separating the 

 two articular faces on the calcaneum, forms a foramen between the bones. 

 On the opposite side of the bone there is a large face set at an angle with 

 the body of the bone, apparently for the tibia. The lower rim of the bone 

 between the described regions has a narrow face for the bones of the tarsus. 

 This ilium was ascribed by Cope to clepsydrops colletii. The form of the 

 bone is shown in Plate IV, Fig. 7, a, b, c, d. [No. 6560.] 



The second type is of stouter proportions than the first and larger ; the 

 articular faces are arranged much the same, but are broader and the face for 

 the distal end of the tibia is more sharply divided into faces meeting at a 

 considerable angle. Plate IV, Fig. 8, a and b. [No. 6561.] 



Neither of these forms corresponds with the figure of the astragalus of 

 Clepsydrops leptocephalns, published by Cope (Proc. Am. Phil. Soc, Aug. 

 1884; Am. Assoc. Ad. Sc. Vol. XXXIII, 1884), nor to an astragalus of 

 Pariotichus incisivus in the collection of the Walker Museum. 



The strong angulation of the tibial face is described by Cope as belong- 

 ing to the genus Dimetrodon, so that it is possible that the larger astragalus 

 in the Illinois material may represent that genus. 



Calcanea. — The calcanea are of the type characteristic of most of the 

 Permian reptiles from America. Large, subround. disks of no great thickness ; 

 the side toward the astragalus presents two facets separated by a notch ; 

 above and below are facets for the fibula (?) and the tarsal bones. Plate IV, 

 Fig. 9, a and b. [No. 6562.] 



Metacarpals and Tarsals. — The metacarpals and tarsals are long and 

 slender, with well developed articular faces. Plate V, Figs. 1 and 2. [No. 

 6563-] 



Phalanges. — -The phalanges show the same well developed form as the 

 preceding row, even to the terminal series. The terminal series are slender, 

 pointed, and curved, and evidently supported strong claws. Plate V, Figs. 

 3-9, and 10, a and b. [Nos. 6564 and 6565.] 



Among the specimens that cannot be referred with certainty 

 to any form are the following: 



