SKULL OF PTERANODON INGENS MARSH. 9 



and side walls. Other specimens indicate that this cavity extended nearly or quite to 

 the point of the mandible. 



The principal measurements of the type skull of P. longiceps, No. 1177, are as fol- 

 lows : 



Length from extremity of sagittal crest to end of premaxillary . . . 720. mm 



Length from occipital condyle to end of premaxillary 630. 



Transverse diameter of occipital condyle 8.4 



Distance from occipital condyle to distal end of quadrate .... 105. 



Length of mandible 570. 



Maximum depth of mandible 70. 



Depth of mandible immediately in front of articulation 26. 



It should be noted that the measurements given by Professor Marsh included the 

 calculated missing portions of the crest and the tip of the jaws. The foregoing meas- 

 urements are taken directly from the skull as preserved. 



SKULL OF PTERANODON INGENS MARSH. 



The type skull of this species, No. 2594, a preliminary notice of which was published 

 by Professor Marsh in the American Journal of Science and Arts, vol. xi, June, 1876, is 

 shown in Plate II, figure 1, Plate III, figure 1, and Plate IV, figure 2. Not only is it of 

 much larger size than the types of P. longiceps and P. occidentalis, but it differs materially 

 in the slope or pitch of the supraoccipital. In the side view of this skull (Plate II, 

 figure 1), it will be seen that a line carried out in extension of the basisphenoid passes 

 through the apex of the supraoccipital plate, which rises less abruptly in P. ingens than 

 in the type skulls of the other species. The basal portion of the crest is accordingly 

 deeper than in P. longiceps. 



Another slight difference between the skulls of P. ingens and P. longiceps is seen in 

 the arrangement of the open network of slender rods of bone forming the lower section 

 of the interorbital septum, where it rests upon the basisphenoid. In P. ingens, the solid 

 upper portion of the septum merges into the open fabric of the lower part. In P. lon- 

 giceps, this transition is more abrupt, and there is a stout and well-defined inferior border 

 to the solid upper portion. It is of course impossible to determine whether this minor 

 difference, drawn from the two skulls only, is of taxonomic importance. Additional 

 material may prove it to be merely an individual variation. The anterior border of the 

 septum divides, right and left, into two branches whose upper ends abut against the 

 under side of the frontal or prefrontal region. This structure is apparently similar to that 

 admirably figured and described by Dr. Plieninger, from a fragmentary skull of Pteran- 

 odon sp., in his memoir entitled : " Beitrage zur Kenntniss der Flugsaurier," but the 

 complete condition of the overlying elements in the roof of the skull here prevents a 

 thorough examination. 



The greatest value of the type skull of P. ingens lies in the excellent preservation of 

 the palatal region. The lower aspect of the skull is similar to that of P. longiceps, as 

 far as the latter is preserved, so that it is necessary to describe in detail only those 

 structures of P. ingens that are lacking in other skulls of the genus. 



To demonstrate the palatal region more clearly, a drawing (Plate IV, figure 2) has 

 been prepared from this unique type skull, and every effort has been made to restore the 



