ON THE SKULL OF NYCTODACTYLUS 529 



is a very large opening, oval in general shape, but with a trian- 

 gular projection behind made by the two inner processes of the 

 pterygoids, and a smaller triangular process in front extending 

 back from the roof of the mouth. It was not divided in the 

 middle and was doubtless covered over for the most part by 

 membrane pierced by the internal nares. 



The skull of Nyctodactylus, while presenting very great 

 resemblances to that of Ornitlwstoma (Pteratwdon) differs in 

 important characters. Its quadrate is much shorter, termi- 

 nating below in the condyle for the mandible nearly below the 

 middle of the orbit, while in Ornitlwstoma the articulation is in 

 advance of the orbit. The orbit and supratemporal vacuities 

 are proportionally larger, and there is no crest, not even a 

 rudimentary one. The bar between the orbit and the nares is 

 narrower, the frontal bone less broad relatively in Ornitlwstoma. 



In Nyctodactylus we have a less highly specialized type of 

 pterodactyl than is seen in Ornitlwstoma as is evidenced by the 

 absence of the crest, the plane frontal bone, and the less oblique 

 position of the quadrate. On the" other hand the genus has the 

 same type of skull, and toothless jaws, and the general propor- 

 tions of the skeleton throughout are the same. I believe that the 

 resemblances between the two genera are of much greater 

 importance than the differences. These differences rest in the 

 non-articulation of the scapula with the supraneural plate of the 

 vertebrae, in the absence of crest, and the position of the quadrate 

 especially. Both forms are toothless. If much importance is 

 given to the scapular articulation the two genera must go into 

 different families at least — Ornitlwstoma among the Ornithochei- 

 ridse, and Nyctodactylus with the Pterodactylidae. But such a sev- 

 erance is, I, believe, questionable. It is a rather curious instance 

 of parallel growth that has brought about the toothless forms 

 of Ornitlwstoma from the toothed Ornithocheirus, and the toothless 

 Nyctodactylus from the toothed Pterodactylus ; possibly this has 

 been the phylogeny. On the other hand, it would also seem 

 possible that the same toothless form has been ancestral to both 



