CRETACEOUS PTERODACTYLES. 389 



In the dorsal region the vertebral centrum (PI. 8, fig. 24), retaining its shortness, 

 gains in depth, and presents the more usual proportions of cup-and-ball reptilian 

 vertebrae. The under surface (fig. 20) is smooth and even, very slightly concave 

 lengthwise, convex transversely. The parapophysis disappears, and the diapophysis, 

 which alone supports the rib, after the first or second dorsal, is sent off from a 

 higher position in the neural arch (fig. 25). 



Sacrum. 



Y 



PI. 8, fig. 26, shows parts of the bodies of three anchylosed sacral vertebrae, 

 the first being demonstrated by part of its anterior concave articular surface (a) 

 for the last lumbar vertebra. The groove for the passage of the nerve notches the 

 back part of the parapophysis, close to the line of suture with the second sacral. In 

 this vertebra the coiTesponding nerve-notch is more advanced, leaving a short sutural 

 surface behind, indicative of a position of the neural arch crossing for a short extent 

 the line of junction of the second with the third sacral centrum. The parapophyses 

 of the second and third are sent off almost on a level with the lower surface of the 

 centrum, which is flattened. 



The fore part of the sacrum of a much larger Pterodactyle, from the Cambridge 

 Green-sand, differing also in the less transverse convexity of the under part of the 

 first centrum, measures 1 1 lines across the shallow anterior articular concavity, and 

 14 hues from the lower part of the centrum to the fore part of the base of the neui'al 

 spine. The neural canal is circular and 2 lines in diameter ; above it the neural arch 

 rises like a vertical wall for 5 lines, where the spine has been broken off. 



Caudal VertehrcB. 



From the number of elongated caudal vertebrae in the series of fossils from the 

 Cambridge Green- sand submitted to me — not fewer than seven — I believe the large 

 Pterodactyle from that formation to have had a long tail, but moveable, not stiff 

 through anchylosis of the vertebrae, as in Pter. {Ramphorhynchus) Gemmingi, V. 

 Meyer. 



The largest of these caudal vertebrae measures 1 J inch in length; it is slightly 

 contracted in the middle ; the fore part of the under surface is a little produced ; the 

 back part almost flat between the rudimental parapophyses ; the shallow anterior 

 concavity has resumed its transversely elliptical shape, and the hinder convexity is 



