mm 



14 OSTEOLOGY OF PTERANODON. 



be required as a counterpoise to the long jaws of Pteranodon, for the form of the 

 cervical vertebrae indicates a strong musculature of the upper part of the neck ; neither 

 the weight of the crest nor its effect as a vertical aeroplane, however, can be entirely 

 disregarded. 



The principal measurements of the type skull of P. ingens, No. 2594, are as follows : - 



Total length of specimen . 840 



Length from occipital condyle to distal end of quadrate 153 



Transverse diameter of occipital condyle (approximate) . . .13 



Depth of mandible immediately in front of articulation 34 



Length of occipital condyle to posterior end of imperfect crest . . 515 



The length of the complete crest of No. 2473, from the center of the occipital condyle 

 to the tip of the crest, is 784 mm. 



SKULL OF PTERANODON OCCIDENTALS MARSH. 



The imperfect skull No. 1179 (Plate III, figure 2) is evidently the one referred to as 

 P. occidentalis in the definition of P. longiceps (Am. Jour. Sci., June, 1876. p. 508), where 

 Professor Marsh stated that the skull of the latter " is somewhat larger than P. occidentalis 

 Marsh, which apparently has more slender jaws." His notes also furnish collateral evi- 

 dence on this point, yet for some reason this specimen was never fully described. No. 1179 

 may therefore be regarded as one of the types of P. occidentalis. Not only is this skull 

 of about the same relative size as the smallest individual of the genus, which fact pre- 

 sumably had much to do with its original reference to P. occidentalis, but it differs 

 materially in form from the type skulls of the two other species. The figure shows that 

 the posteriorly directed face of the supraoccipital rises more sharply in this species than 

 in the type of P. longiceps, in this regard the difference between P. occidentalis and 

 P. ingens being even more striking. The supraoccipital crest is smaller than in the type 

 skulls of other known species, and the curved and regular form of its superior margin 

 favors the supposition that it is here practically complete, while in P. ingens, No. 2594. and 

 P. longiceps more or less of the crest has been lost. 



The apparent slenderness of the jaws alluded to by Professor Marsh is not an alto- 

 gether satisfactory character. While it is true that in its present condition the left man- 

 dibular ramus is not so deep immediately behind the symphysis as are the same parts of 

 P. longiceps and P. ingens, there is some doubt whether the inferior margin of the mandible 

 may not have been broken away at this point. If the rami were no deeper immediately 

 behind the symphysis than this fragment indicates, it would appear impossible for the 

 transverse diameter of the mandible to approximate the corresponding measurement of 

 the maxillary arch. The angular part of the mandible posterior to the articulation is 

 missing, and the connection between the maxillary arch and the basal portion of the 

 skull has been destroyed. With the exception of the points of difference already men- 

 tioned, the skull in its general form is similar to those of the other species. 



Measurements of Skull No. 1179. 



Distance from occipital condyle to distal end of quadrate . . . . 75. mm 



Distance from occipital condyle to apex of supraoccipital surface . . . 46. 



Diameter of occipital condyle . . , . 7.5 



