On the Osteology of Nyctosaurus. 129 



surface is oval, the plane of each nearly at right angles with that of its mate. 

 The spine is broad and transverse; from the front it presents a median 

 ridge. On the under side the centrum is flat, the flatness reaching nearly 

 to the extremity of the parapophysis ; the width is considerably greater 

 than the length. The posterior surface of the centrum in this specimen 

 is distinctly roughened for sutural union with the following centrum; the 

 posterior zygapophyses also unite with the succeeding ones suturally. 

 This vertebra is very clearly the first of the notarium, as Seeley has hap- 

 pily called the united dorsal vertebrae. " Two other vertebrae found close 

 by the one described, and possibly one or the other contiguous with it, 

 differ remarkably in having no or a rudamentary parapophysial process, 

 and in having the diapophysis much shorter." "In Pteranodon there are 

 at least four vertebrae with dia- and parapophyses." " In two other 

 centra there is a long, recurved, parapophysial process, as though formed 

 by an anchylosed rib, on each side; they are probably lumbar vertebrae." 

 It is very clear, however, that these last two vertebrae are not lumbars, but 

 separated elements of the notarium. Of the two other vertebrae men- 

 tioned, one is probably the eighth cervical, described below, while the 

 other may be the fourth dorsal. 



In Pteranodon, I thought there might be two vertebrae intervening 

 between the elongated cervicals and the notarium. " The centrum is short 

 and broad, so different from the preceding one that it is possible there 

 may be an intervening one lost. The ball is more than four times as 

 broad as high, concave on the upper margin, convex below. The post- 

 exapophyses are large, and confluent with the articular faces of the ball, 

 but are concave. The convex pre-exapophyses, at the outer side of the 

 cup are at the base of the lower root (that is the parapophysis) of the 

 elongated transverse process."* This vertebra corresponds with the 

 eighth post-cranial vertebra of the present specimen, but an "imperfect 

 vertebra, evidently following the one described, has the centrum very simi- 

 lar, save that the spine appears to be less stout." I cannot at the present 

 time examine this specimen, but it is probable that it is the first separated 

 vertebra of the notarium. 



From the foregoing, then, it seems assured that there is a free, short 

 vertebra in front of the notarium, in both Pteranodon and Nyctosaurus, 

 bearing a free, small rib, which does not unite with the sternum. This ver- 

 tebra is the eighth cervical, and is probably present in all pterodactyls. It 

 is strange that authors, in the description of the neck bones of the ptero- 

 dactyls should have so often spoken of the united atlas and axis as one 

 vertebra, thus reckoning seven instead of eight vertebrae in this part of the 



* Williston, Kansas University Quarterly, vol. vi, p. 40. 



