LIASSIC PTERODACTYLES. 469 



haemapopliysis from the acetabulum.i The ischium seems to contribute the hirger share 

 of the acetabuhun in Bimorphodon, PI. 16, «. In Birds, as in Lizards, the pubis forms 

 part of the acetabular cavity.^ 



In the specimen, PI. 16, a portion, cd, of a long tail, of which the vertebrae were 

 smTormded by numerous slender bone-tendons, extends backward and downward beyond 

 the pelvis : a better preserved portion with three caudal vertebrae (c d!) is preserved in a 

 detached part of the matrix found in the vicinity of the larger slab. Ikit to this part of 

 the vertebral column I shall return in describing the more perfect specimen of the tail of 

 Dimorphodo?}, from another individual. 



Behind the skull are four cervical vertebrae (PI. IG, c), and part of a fifth in natural 

 juxtaposition, or perhaps a little separated at the articular surfaces. The under surface of 

 the centrums and articular processes of the neural arches are exposed. The sides of the 

 centrums show a slight concavity, but their crushed state obscures the natural contour of 

 the under surface. The hind part of the under surface, in the last two of these 

 vertebrae, shows a pair of low obtuse processes, with an indication of a convex terminal 

 articular surface. The centrum expands in breadth as it advances, and sends out a short 

 thick process (parapophysis) from each side of the fore part ; to which, in the last three 

 vertebrae, are indications of attachment, or parts, of a backwardly produced styliform rib. 

 At the midline of the fore part of the last two of these vertebrae a fracture indicates a 

 ridge or process there to have been broken off. The pre-zygapophyses are thick, and project 

 far in advance of the concave anteiior articular surface of the centrum : the convex 

 posterior articular surface of the centrum projects as far beyond the post-zygapophyses. 

 Their joints are more vertical than horizontal : the posterior surfaces looking slightlv 

 outward and downward. 



The superior breadth of the neural arch, as compared wMth that of the centrum, 

 brings its articular processes into view, along each side of the vertebral bodies, in the 

 degree shown in PI. 16, c. The character of the articulations indicate less extent and 

 freedom of movement of the cervical vertebrae than in Birds, and more restriction in the 

 lateral than in the vertical directions. The interlocking joints resulting from the different 

 lengths of the fore and hind articular processes add strength to the part of the spine 

 supporting the head. 



The cervical vertebrae of Dimorphodon, so far as their structure is exemplified in the 

 present specimen, conform to the pterosaurian characteristics of these vertebrae, as shown 

 in those of Pterodadylus /S'e(^?OTe/fM, described (p. 382), and figured in PI. 7, figs. 7 — 18 ; 

 and in those of Pterodadylus simus (p. 437, PI. 11, figs. 1 — 5). 



The skull presei-ved in the present specimen agrees in size with that in the slab pre- 

 viously received (PL 15), repeats the characteristics of the genus Bimorphodon, and shows no 



1 'Anatomy of Vertebrates,' vol. v, p. 188, fig. I 19. 



2 lb., p. 190. 



