SKULL OF PTERANODON LONGICEPS MARSH. 5 



this bird lacks the perfect spiral groove and thread characteristic of the quadrate and 

 articular of Pteranodon, the modeling of these bones seen in the prepared cranium forms 

 an effective screw that thrusts apart the mandibular rami when the mouth is opened. 

 That the spiral articulation is directly concerned in the widening of the mouth of both 

 Pteranodon and the Pelican, there can be little doubt. In the Pelican, however, this 

 skeletal modification may have arisen as a result of the peculiar musculature of the 

 lower jaw referred to by Dr. Coues (Key to N. A. Birds, p. 721). The reference, which 

 is not original with Dr. Coues but quoted from another author whose name is not given, 

 is repeated here : " When the bill is opened, the crura of the lower mandible separate 

 from each other to a considerable extent [in their continuity not at the symphysis], by 

 the action of muscles inserted into their base, and the sac is expanded." Possibly the 

 mechanical similarity between the suspensorium of Pelican and Pteranodon should be 

 received as evidence of the possession of a gular sac by the pterodactyl also. This 

 would be in harmony with the views of Mr. F. A. Lucas, who stated (Ann. Rept. Smith- 

 sonian Inst. for 1901, p. 657): "In the peculiar shape of the lower, back portion of the 

 beak there is a suggestion of the former presence of a small pouch, like that found in 

 cormorants, and this would be in accord with the supposed fish-eating habits of Ornitho- 

 stoma" (Pteranodon Marsh). 



Maxillary Arch. 



In this skull no demarcation is shown between the premaxillse and maxillae, and here 

 as well as in the type of P. ingens, to be described later, the maxillo-jugal sutures are 

 entirely obliterated. A skull of Pteranodon sp. in the Museum of the University of 

 Kansas shows a long splintlike development of the jugal overlapping the maxilla on its 

 outer surface and extending forward to a point beneath the anterior end of the narial 

 vacuity. This is quite in accord with Professor Williston's view as to the position of 

 the suture in question, expressed in his paper : " On the Skull of Nyctodactylus." Pecu- 

 liar breaks occur in the types of P. longiceps and P. ingens, nearly beneath the centers 

 of the antorbital vacuities. At first glance, these seem to indicate the position of the 

 maxillo-jugal sutures, but it is much more probable that they are merely fractures caused 

 by pressure, this part of the maxillary arch being subjected to an unequal strain, owing 

 to the partial support afforded by the transpalatine bone. 



Palato-pterygoid Arch. 



The extraordinary form of the palatines and pterygoids, together with their associated 

 elements, is one of the most striking characters of Pteranodon, and still further sepa- 

 rates the genus from other groups of the Pterosauria. 



Although certain important parts are yet wanting in the type skull of P. longiceps, 

 careful and persistent work on this specimen has resulted in considerable advance in a 

 knowledge of the palatal region. The complete demonstration of the bony palate will 

 be found on page 9, where the type skull of P. ingens is described in detail. The pecu- 

 liar form of the bones of the palato-pterygoid arch here described is based on these 

 elements as preserved in the type of P. longiceps and also in another skull, No. 2440, of 

 about the same size. 



Stout transverse buttresses of bone about 3 cm in length extend outward and slightly 

 downward from the anterior extremity of the basisphenoid, fusing at their distal ends 

 with the quadrates, which they support in the strongest manner. The inner ends of 



