32 OSTEOLOGY OF PTERANODON. 



of this joint viewed from the palmar side, figure 5 has been made from the conjoined frag- 

 ments of the left metacarpal and the first phalanx of Pteranodon sp., No. 2660, which 

 are crushed vertically. The bones are here represented in actual contact, with the joint 

 extended just as preserved in the matrix. Figure 6 shows these same parts when separated. 



The distal end of the first phalanx of the wing finger, as described by Marsh, "presents 

 an elliptical, convex, articular face, which does not entirely cover the distal surface. The 

 second phalanx has its proximal extremity adapted to this articular face by a shallow 

 elliptical cup, which does not extend over the most proximal portion of the extremity. 

 The distal end resembles in everything but size the corresponding part of the first 

 phalanx. The next or third phalanx is quite similar to that which precedes it, except that 

 it is more attenuated. The slender terminal .phalanx appears to have been more nearly 

 circular at its proximal end, although apparently compressed toward its other extremity. 

 The articular surfaces of all the bones preserved are smooth and well defined, like those 

 of mammals and birds. All the bones of the wing, moreover, even the carpals, appear to 

 have been pneumatic." The shafts of the wing bones generally are of extreme tenuity, 

 fragments from some of the larger specimens having only a thickness of one millimeter. 



From the form of the articulation, it is evident that the flexion of these phalanges 

 upon each other was limited to an angle of about 45. When the wing was fully ex- 

 tended, it is probable that the flexion of these bones upon each other was very slight. 

 In Plate XXV, figures 1-7, the wing bones preserved in Pteranodon sp., No. 2452, have 

 been arranged so that the relative lengths of the phalanges may be seen. The wing 

 bones preserved in another individual, No. 2774, are displayed in Plate XXVI, figures 1, 

 2, and 3. The fourth or terminal phalanx is missing in this example, but is preserved 

 in No. 2470 (Plate XXVI, figures 4-7) and No. 2591 (Plate XXVI, figures 8 and 9). The 

 curvature of the fourth phalanx of the wing finger, which is clawless, varies slightly in 

 different individuals, and indeed is not precisely the same in the right and left wings of 

 one of the few examples in which both members are preserved. In no specimen in the 

 Marsh Collection is this bone straight. The pteroid bone, lacking its proximal articula- 

 tion, might easily be mistaken for a terminal phalanx. In face of this evidence, it would 

 appear unwise to attempt to separate species on slight differences of curvature in the 

 terminal phalanx of digit V. 



From twenty-five examples of Pteranodon in the collection, linear measurements of 

 various wing bones have been taken, and are presented in Table A. In Table B, each 

 of the first five sections of the wing has been taken in turn as the unit of length, the 

 lengths of the other bones being expressed as percentages. The original purpose of 

 these tables to aid in separating the species is in large measure foiled by the imper- 

 fection of the material. Perhaps their greatest value lies in the indications they afford 

 as to the size attained by the genus. 



For convenience, the measurements of the femur and tibia have been included in these 

 tables ; and at the bottom of Table B, the comparative measurements of the wing bones 

 of P. ingens given by Professor Williston in his paper : " On the Osteology of Nycto- 

 saurus " have been entered. These measurements, as stated in a letter from Professor 

 Williston, were " taken from a life-sized drawing made of the mounted specimen in the 

 Kansas Museum." It now seems impossible to prove positively that the wing bones 

 referred to belonged to a single individual ; for the Curator having charge of the col- 

 lection writes : " I find that in some cases the bones have been mounted on wires, etc., 

 and that the catalogue number must have been either erased or is underneath." On 



