14 AMERICAN PERMIAN VERTEBRATES 



vertebral spine. The plate is gently and evenly convex above, 

 slightly convex on the anterior thinned border, and correspondingly 

 concave on the posterior thicker border. The upper surface is 

 rather deeply marked by irregular pits and grooves, as is seen in 

 the photograph. It is very evident that the plate did not overlap 

 the preceding plate, as is the case in A. chiton Broili, the genotype. 

 In the middle behind, however, the flat surface of the spine served 

 to help support the following dermal plate. 



Associated with this plate in the bone-bed are a considerable num- 

 ber of femora, and several humeri of the types figured and described 

 by me in the Bulletin of the Geological Society of America, XXI, 

 270, Plate XV, Figs. 4, 5. The most typical specimens of the 

 femora found associated with the type are shown natural size in 

 Plate XXXIII, Figs. 1-4, and Plate XXXII, Figs. 4, 6. While all 

 these femora have the same general shape and high adductor crest, 

 and the same absence of condylar ossification, they differ very 

 materially in their slenderness, especially noticeable in Plate 

 XXXII, Fig. 4, and Plate XXXIII, Fig. 3. That one or the other 

 of these femora and one or the other of the types of humeri figured 

 in the cited paper belong with the species represented by the 

 dermal plate is quite sure, but, as it is impossible to determine 

 which of them should bear the name A. peltatus, the dorsal spinous 

 expansion shown in the figure may be considered the type of the 

 species. The species seems nearest related to A. glascocki Case, 

 but differs materially in the character of the sculpture, the thickness 

 of the plate, and the relations of the vertebral spine itself. 



There are various small intercentra in the collection, and frag- 

 ments of jaws, which doubtless belong with one or the other of the 

 species represented by the humeri and femora. 



