132 Field Columbian Museum — Geology, Vol. II. 



lying upon their ventral surface, that is, compressed dorso-ventrally, and 

 two were more or less crushed laterally or obliquely. There is less 

 difference in the lengths of the five following the axis than is the case in 

 Pteranodon ; I am therefore somewhat in doubt as to the precise position 

 of some of them. Those that are depressed have the under surface 

 irregularly plane or concave, with the lateral margins rounded and 

 concave, formed by the ridge which reaches from the anterior zygapo- 

 physis and exapophysis on each side to the corresponding posterior 

 exapophysis. At the front margin there is an oval fossa, or depression, 

 on each side, separated by a convex surface; this convexity seems often 

 to be produced into a distinct hypapophysis in the European pterodactyls. 

 In a previous paper I stated that the exapophyses are non-articular in this 

 genus. This statement, after a more careful examination of the speci- 

 mens removed from the matrix, I know to be erroneous, at least so far 

 as the processes of the posterior vertebrae are concerned. Owen has 

 identified these processes with the parapophyses, and Plieninger prefers 

 to adopt this name for them. As will be seen by an inspection of Fig. 

 7, PI. XLIII, the true parapophysis — that is the process for the articulation 

 of the head of the rib, for which the term was originally introduced by 

 Owen, and in which sense it is now used — is always situated at the anterior 

 end of the vertebra, close to the rim of the cup. This process bears on 

 its anterior face, close to the rim of the cup, a convex, articular surface 

 for union with the corresponding concave surface of the " posterior 

 parapophyses " of the preceding vertebra. One might with as 

 much propriety call these posterior prominent articular processes the 

 diapophyses, or posterior inferior zygapophyses, as " posterior para- 

 pophyses." There is no such thing as a posterior parapophysis, nor can 

 there be. Nor could these posterior "parapophyses" ever have arisen 

 as processes for rib articulation. They are very characteristic of the 

 pterodactyl vertebrae, taking the place of the lateral or double articula- 

 tion of the cryptodire testudinate cervical vertebrae. I have given these 

 articulations a distinctive name of exapophyses in order to save much 

 circumlocution in their description; in any event they should not be 

 called "parapophyses," since they have nothing to do with these processes, 

 either morphologically or functionally. 



The cup and ball are widened transversely; in the depressed specimens 

 very much so, and this is not due to their crushing, since those lying upon 

 their sides, though mutilated, still preserve evidence of a lateral elonga- 

 tion of the articular surface. The convexity of the ball is marked dorso- 

 ventrally, more so near the neural side. The posterior border between the 

 exapophyses is thin and concave, nearly concealing the ball, when seen 

 from below. The anterior zygapophyses project much in front of the cup; 



