SKULL OF PTERANODON LONGICEPS MARSH. 3 



the distal ends of both tibiae, together with the right tarsus. The skeleton to which 

 they belonged was of about the size of P. occidentalis. No. 1164. Associated with these 

 types in the collection is No. 2397, which is clearly composed of parts of two individ- 

 uals, because the distal end of the femur and the distal end of the tibia, with frag- 

 mentary metatarsals included under this number, are of incompatible size. The tibia 

 evidently belonged to an individual of about the size of the type of P. occidentalis, 

 No. 1164, while the femur is that of a slightly smaller animal. It is a matter of con- 

 siderable surprise to find that the measurements of the distal end of this tibia exactly 

 equal those given by Professor Marsh for the distal end of the wing metacarpal, in his 

 specific definition. The peculiarly crushed distal end of the tibia looks wonderfully like 

 the distal end of the wing metacarpal, and Professor Marsh may have confused the two 

 at a time when the osteology of pterodactyls was little understood. The only course 

 open under the circumstances is to regard P. comptus as no longer valid. 



P. nanus clearly does not belong in the genus Pteranodon and may be referred to 

 Nyctosaurus. 



The collection also contains many incomplete specimens of doubtful specific identity, 

 which have proved of considerable value in determining the characters of the genus. 



SKULL OF PTERANODON LONGICEPS MARSH. 



The nearly complete skull of Pteranodon longiceps Marsh, No. 1177, which was origi- 

 nally described as the type of the genus * and later more fully discussed and figured, 2 

 is shown in Plate I, figure 1. The result of further investigation has been to reveal new 

 structure rather than to discover inaccuracies in Professor Marsh's preliminary work, 

 which was necessarily somewhat incomplete. The purpose of the present memoir will 

 therefore be best served by making free use of original definitions as far as they have 

 proved correct, while new structure may be properly described in detail. 



It should be noted that fusion of the elements has resulted in almost complete oblit- 

 eration of the cranial sutures in this genus. The terminology of the skull is therefore 

 somewhat lax, and must at times refer to the regions usually occupied by these elements, 

 their exact limits being indeterminable. 



The head was remarkably long in proportion to its width, and in this respect Pterano- 

 don probably surpassed all other vertebrate animals. The skull is greatly produced in 

 the axial direction, the attenuated jaws continuing forward into long sharp points, while 

 the enormous sagittal crest extended far backward over the cervical region. The mar- 

 gins of the jaws are smooth and thin, though not especially sharp, and no remains of 

 horn sheaths have been observed. 



Under Side of Skull. 



The occipital condyle is small, its smooth rounded surface forming more than a hemi- 

 sphere. It is directed downward and backward at an angle of about 45 with the 

 palatal axis of the skull, and is separated by a slightly constricted neck from the main 

 part of the basioccipital bone, which is represented by an irregularly oval plate about 



1 Am. Jour. Sci. (3), vol. xi, p. 507, June, 1876. 



2 Ibid., vol. xxvii, p. 423, pi. xv, May, 1884. 



