LEG BONES. 35 



LEG BONES. 



The femur of Pteranodon ingens has been amply described by Professor Williston 

 in the following paragraph (On the Osteology of Nyctosaurus, p. 150), which will be 

 found to agree well with the form of the bone as shown in Plates XXVII, XXVIII, 

 and XXIX: — 



" The convexity of the head is regular, covering nearly half of a circle transversely, 

 probably a little less in the conjugate diameter, the surface thus forming an oval or 

 ovate figure, the plane of whose base is nearly at right angles to the long diameter of 

 the bone. The convex surface is sharply limited from the neck. The neck is cylindrical, 

 rather stout, and is directed nearly vertically downward. The rounded and moderately 

 prominent trochanter is placed over the middle of the shaft, descending into the con- 

 cavity at the side of the neck, and externally separated from the margin of the bone. 

 The shaft is nearly of equal width throughout ; doubtless in life it was nearly cylindrical, 

 with a strong anterior curvature, and a flattening in the popliteal region. The sharp 

 margin of the inner condyle encompasses nearly half a circle. The outer condyle, 

 though extending further, is much less in extent. The inner distal articular surface is 

 the larger, and is separated from the inner surface by a distinct ridge, especially 

 posteriorly." 



Professor Williston's description of a tibia of Nyctosaurus immediately following the 

 above quotation applies equally well to the tibia of Pteranodon, showing how closely 

 the leg bones of these two genera resemble each other. His words are as follows : — 



" The tibia is a slender, straight bone, moderately expanded at the upper extremity. 

 The margin of the articular surface above is nearly transverse to the longitudinal axis. 

 The width contracts chiefly at the expense of the posterior margin to the lower part 

 of the upper fourth of the bone, the shaft below being of nearly uniform width. The 

 trochlear surface at the distal extremity is pulley-shaped, covering about half of a circle, 

 perhaps more, and has a moderately deep groove." Professor Williston adds : ' l There 

 is no trace of any fibula, either in the preserved remains or in any tibial articulation." 

 This is also true of the Pteranodon material contained in the Marsh Collection. 



Of the leg bones of P. ingens (type), No. 1175, only the right femur (entire), the 

 proximal end of the left femur, and the proximal and distal ends of the right tibia are 

 preserved; the bones of the right leg are shown in Plate XXVII, figures 4, 5a, and 5b. 

 The two femora and their tibiae of a slightly smaller individual of Pteranodon sp., 

 No. 2738 (Plate XXVIII), will be found similar to those of P. ingens (type), as are also 

 the leg bones of Pteranodon sp., No. 2489, which are figured on Plate XXVII, figures 1, 

 2, and 3, together with the partially complete set of podials found with them. The leg 

 bones of a still smaller individual of Pteranodon sp., No. 2493, are shown in Plate XXIX, 

 with the nearly perfect right tarsus and metatarsus. The state of preservation of the 

 two tarsals is such that it is now impossible to fit these bones accurately together in 

 contact with the tibia and metatarsus. In this plate, they are shown as found in the 

 matrix, a little removed from their natural position. The stout claw-shaped bone asso- 

 ciated with them is supposed to be the rudimentary fifth metatarsal. In the illustration 

 of the right foot of No. 2502 (Plate XVI, figure 1), the tarsals are figured from the 

 proximal surface. The claw-shaped fifth metatarsal is preserved, and distinctly shows 

 the articular facet on its proximal end. Unfortunately, these three bones are so badly 



