Permian of New Mexico. 397 



or Pelycosauria. The tibiale, or intermedium, is nearly 

 cuboidal in shape, with a slight notch only between the articular 

 faces for the tibia and fibula. Its outer facet is thickened for 

 union with the fibulare, but I see no perforating foramen 

 between the two bones. The distal and inner facets are also 

 very broad, subquadrate in outline, with rounded angle. The 

 fibulare is a larger bone, but much thinner than the tibiale ; its 

 tibial side is the thickest. I identify these two bones as the usual 

 fused tibiale and intermedium, and the fibulare, but it is not 

 impossible that the tibiale has been entirely lost, after fusion, 

 and what really remains are the intermedium and fibulare. 

 I have so far found no evidence satisfactory to me that the 

 tibiale and intermedium are ever present in adult reptiles as 

 distinct bones. I am aware that Broom has provisionally 

 recognized a separate intermedium in Howesia and that other 

 instances have been cited, but 1 think they are all open to 

 doubt. The separation of the intermedium of the hand is a 

 very persistent character in the Amniota, Man, himself, even 

 having the same bones that are found in the temnospondyls in 

 the proximal row of the carpus. In the tarsus, however, there 

 was an early specialization, as far back as early Carboniferous 

 times, and I do not think there was ever a reversion to the 

 amphibian type. 



Of the left foot of specimen 908 only these two tarsal bones 

 and a number of separated toe bones have been recovered. Of 

 the right foot, however, all the bones of the toes were preserved 

 in their natural relations in the matrix, or with but slight dis- 

 tortions, the metatarsals all lying in one plane, apparently quite 

 in the positions they occupied in life. The block containing 

 them had the phalanges of the first toe, the first one of the sec- 

 ond toe, the first two of the third toe and all four of the fifth 

 toe in close articulation, those of the first and fifth toes strongly 

 flexed. With this block, but separated, were the phalanges of 

 the middle toes, the two each of the second and third and all 

 five of the fourth toe severally connected by matrix," but not 

 positively attachable to the basal bones of their respective dig- 

 its, because of the effacement of the matrical surfaces in collect- 

 ing. That they belong with these toes is, however, beyond 

 doubt, both because of their perfect anatomical association and 

 the peculiarities of the matrix. The formula as is thus seen is, 

 like that of the front feet, the primitive one for reptiles, 2, 3, 

 4, 5, 4. The phalanges, as of the front feet, are all remark- 

 ably short and broad, and I may also add, relatively thin. The 

 ungual phalanges, as have been described for Diadectes, which 

 they resemble, are short, broad and hoof-like rather than claw- 

 like, with a thin rounded extremity, the bones possibly encased 

 in a horny nail in life. I can hardly conceive of a foot of this 

 character being used for burrowing, notwithstanding Case's 



