DORSAL VERTEBRA. 17 



ters. The centrum of the ninth cervical bears no hypapophysis. The articular facets 

 of the postexapophyses of the eighth and ninth cervicals remain much the same as in 

 the vertebras preceding them, but there are no posteriorly directed processes below these 

 facets. Instead of curving backward in the bladelike form characteristic of the third to 

 the seventh cervicals, the neural spines rise straight upward and are abruptly truncated 

 at their full height. When these vertebras have been crushed in the axial direction and 

 the thin neural spines have been destroyed, the stout processes, termed by Williston 

 metapophyses, assume the appearance of bifid spines. 



DORSAL VERTEBRiE. 



In a short paper entitled : " Note on American Pterodactyls " (Am. Jour. Sci., vol. xxi, 

 April, 1881), Professor Marsh wrote : " To aid the powerful wings [of Pteranodon] in 

 flight, the pectoral arch is strengthened, (1), by the ankylosis of several vertebras; (2), by 

 the robust scapulas articulating on opposite sides of the common neural spine of these 

 vertebrae." This brief description was accompanied by a foot-note calling attention to 

 a similar structure in some of the English Cretaceous pterodactyls also. Following this 

 suggestion, Professor Seeley published an instructive paper: "On the Shoulder-girdle 

 in Cretaceous Ornithosauria" (Ann. Mag. Nat. Hist., May, 1891), in which he described 

 the structure in Ornithocheirus Seeley, and figured a composite restoration of three dorsal 

 vertebras united by a " supra-neural ossification," with lateral facets for the scapulas. 

 The Marsh Collection contains several more or less perfect examples of the anterior 

 dorsal or notarial vertebras of Pteranodon. These have been carefully prepared in order 

 to ascertain, if possible, the exact number of anchylosed vertebras and their form. The 

 best preserved notarium is that of Pteranodon sp., No. 2692. Photographic views show- 

 ing the actual condition of the left and right sides may be seen in Plate VII, figures 1 

 and 2. Attention should be called to the fact that the last cervical is still in contact 

 with the notarium. The slight dislocation it has suffered is apparent only in the view 

 from the right side. Obviously, to separate this ninth cervical from the notarium would 

 necessitate destroying its delicate rib. While this specimen is by no means complete, 

 it is possible, by supplying the missing portions of one side from those preserved on the 

 other, to reconstruct accurately the original form. Figures 1, 2, 3, and 4, of Plate VIII, 

 have been made in this way to show the notarial vertebras as seen from the left side, 

 from the front obliquely, from above, and from below, respectively. These diagrams are 

 slightly at fault in that they represent the ribs as issuing nearly at right angles to the 

 vertebral column ; the ribs were probably directed a little posteriorly. The most impor- 

 tant characters of this series of vertebras in No. 2692 are as follows : — 



The centra of the eight anterior dorsal vertebras are firmly coossified. The dorsal 

 spines are bound together and surmounted by a thin median ossification, the supraneural 

 plate, which is fused with their upper extremities. The vertical depth of this median 

 ossification is greatest above the interval between the third and fourth dorsal spines, 

 where on each side it presents an oval facet for the lodgment of the upper ends of the 

 scapulas. These eight vertebras are also bound together by paired ossifications that 

 extend the length of the notarium, fusing with the ends of the transverse processes in 

 the same manner that the supraneural ossification unites with the dorsal spines. The 

 centrum of the first dorsal is the largest of the series. Its length and breadth are about 



