8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I39 



especially prominent and extends proximally nearly in line with the 

 femoral head. Ossification is fully developed in the femur as well as 

 in the more distal elements. 



The tibia and fibula are short, stout bones of generally primitive 

 contour ; the fibula appears relatively more massive than is usually 

 the case in the tetrapod limb. The distal end of the left tibia appears 

 to have slipped slightly upward from the life position and now rests on 

 the neck of the astragalus. Otherwise, the left femur, tibia, and fibula 

 are in normal articulation. 



The right pes is twisted so as to obscure details of the tarsus, but 

 details of the digits help to complete a restoration of the left pes. The 

 left pes is preserved dorsal side uppermost and exhibits one of the 

 most perfect preservations of tarsal structure known from the Car- 

 boniferous, indeed, from the Paleozoic, as will be demonstrated pres- 

 ently. The pes has been given several superficial descriptions (Cope, 

 1897; Williston, 1908; Moodie, 1909) which fail to recognize the ex- 

 tent of ossification in the tarsus, but nevertheless establish two proxi- 

 mal elements in the tarsus and a phalangeal formula of 2-3-4-5-4. A 

 main difficulty lies in the interpretation of tarsal elements distal to the 

 presumed astragalus and calcaneum, especially in the medial region 

 of the tarsus where no one has been able to recognize central elements. 

 Moodie's figure (1909, pi. 5), republished by Case (1911), is particu- 

 larly misleading in that the tarsus appears to have an enigmatic pat- 

 tern, doubtfully reptilian. (Also, in Moodie's figure a nonexistent 

 element is added distal to the lateralmost distal tarsal, although none 

 is shown in Moodie's retouched photograph — his pi. 4). My photo- 

 graphs (pi. 1 A, B), taken under low-angle light from first one direc- 

 tion and then from the opposite direction, demonstrate the wealth of 

 detail making possible text figure 2. The two proximal bones of the 

 tarsus are clearly the astragalus and calcaneum which enclose between 

 them a perforating foramen, not previously noted. The astragalus 

 has a small but definite tibial facet directed mostly preaxially. There 

 is no evidence of tripartite structure such as exhibited by Captorhinns 

 (Peabody, 1951). The preaxial border between the astragalus and the 

 first metatarsal clearly exhibits two bones that must be a median cen- 

 trale and distal tarsal 1. A thin veneer of matrix obscures part of 

 the dorsal surface of these bones, but the oblique lighting (pi. iA) 

 clearly brings out their contours in the preaxial border. Lateral to 

 these bones and median to the large distal tarsal are at least 2 and 

 probably 3 separate bones that are identifiable as the lateral centrale 

 and distal tarsals 2 and 3. A slight proximal jamming (see fig. 2) has 



