2 OSTEOLOGY OF PTERANODON. 



only entire skeletal element common to the two types, and he evidently distinguished 

 these species by their marked difference in size and by supposedly contrasting charac- 

 ters ascribed to the humeri and to the proximal ends of the ulnae. 



While it might be expected that the great difference in size of P. occidental and 

 P. ingens would be accompanied by some minute but reliable differences in the form of 

 the wing bones, recent careful work by the preparator has not proved such to be the 

 case. On the contrary, the slight differences in the form of the humeri and of the 

 proximal ends of the ulnae, noted by Professor Marsh, now appear to be due entirely to 

 extraneous causes. To the critical reviewer of Professor Marsh's early work on this 

 subject, it is evident that the two skulls referred by him to P. ingens and P. occidentalis 

 were specifically identified by their size alone. There can have been no other reason 

 for associating them with the skeletal parts belonging to the original types of the two 

 species. 



That such action was arbitrary, can not be disputed, yet it was in accordance with 

 the established usage of Paleontology, and the ultra-critical course of denying the specific 

 identity of these two skulls would be equally arbitrary and would involve the subject 

 in still greater uncertainty. It seems advisable to let this part of Professor Marsh's work 

 stand unchallenged, and to attempt the separation of the Pteranodon material in the 

 collection into three species by slight but fundamental differences displayed by the skulls. 



P. velox was based upon the distal end of the right metacarpal of the wing finger and 

 the proximal end of the adjoining first phalanx. It now appears that the form of this 

 fragmentary metacarpal is considerably altered by an attached concretion of foreign 

 matter; otherwise it and the proximal end of the first phalanx differ no more in form 

 from the same portions of the types of the foregoing species than is to be expected in 

 view of the crushing they have undergone. 



P. longiceps is represented by a nearly perfect skull, No. 1177, with atlas and axis, 

 which offers striking similarities to the skull of P. ingens, but is only about two-thirds 

 its size. The matrix was not thoroughly removed from the skull of P. ingens until after 

 Professor Marsh's death, and it appears that the difference in size recorded by him was 

 the only comparison of these two species possible under the circumstances. Professor 

 Marsh regarded the skull of P. longiceps as the type of the genus Pteranodon, and it 

 seems especially desirable that this species be retained. Its distinction from P. ingens 

 can be accepted without too great difficulty, in view of the marked contrast in size 

 accompanied by the slight structural differences noted in the following pages. Obviously, 

 it is impossible to differentiate a species represented by the skull only from another 

 species represented by wing bones only, but by accepting Professor Marsh's choice of 

 the fragmentary skull No. 1179 as a type of P. occidentalis, it becomes possible to com- 

 pare that species with P. longiceps. 



P. comptus, which was described in the American Journal of Science, vol. xi, June, 1876, 

 is untenable. It was based upon portions of three skeletons in the Yale Museum, and 

 was defined by Professor Marsh as " the smallest Pterodactyle known from American 

 strata." The types were said to include distal ends of two fifth metacarpals, the distal 

 end of the ulna, and two sacral vertebrae. Of the three supposed individuals referred 

 to this species, No. 2287, marked " P. comptus, type in part," consists of two posterior 

 dorsal centra detached from their neural arches. They are smaller than the correspond- 

 ing parts of any example of Pteranodon known to the writer, and should perhaps be 

 referred to Nyctosaurus. No. 2335, also labeled "P. comptus, type in part," comprises 



