7iJ 



5. W. WILLISTON 



in the skull of Nyctosaurus and Pteranodon, the American Cretaceous 

 pterodactyls. This would suggest that the supposed elongated basi- 

 sphenoid of Nyctosaurus is really the parasphenoid, against which view 

 we have the improbabihty of the survival of so large a parasphenoid 

 in this type of reptiles, as well as the mode of attachment of the ptery- 

 goids on either side. 



The junction of the transpalatine is seen in the specimen on the 

 left side, but the shape and relations of the bone are obscured by the 

 mandible, though certainly there is no posterior palatine foramen; 

 doubtless the relations of the bone are quite as I have figured them 

 in T. osborni. 



The relations of the pterygoids posteriorly cannot certainly be made 



Fig. 5.^ T. hentonianum. Section through basioccipital and parasphenoid, one- 

 half natural size. BO basioccipital; BS, basisphenoid; PS, parasphenoid; PT, 

 pterygoid. 



out in skull "No. 2" nor were they in the type of T. osborni. Very 

 fortunately, however, the posterior part of skull "No. i," the type 

 specimen of the genus, gives nearly all the information that could be 

 desired. In this specimen there is a longitudinal break or split 

 through the occipital condyle, nearly in the middle hne, to the inter- 

 pterygoidal vacuity. I give this section in fig. 5. The distinction 

 between the basioccipital and basisphenoid is not clear, but it must 

 be as in T. osborni or nearly so, as has been indicated by the broken 

 lines of the figure. In front of the basisphenoid the conical and 

 thickened parasphenoid, or "presphenoid" narrows into a median, 

 long, and vertically broad bone to the hind end of the interptery- 

 goidal vacuity, which it bounds. Posteriorly it extends, by a squa- 

 mous underlap, nearly to the hind margin of the basioccipital, the 



