544 BRITISH FOSSIL REPTILES. 



§ 3. Pterosatjria of the Kimmeridge Clay. 

 A. — Fierodactylus Manselii, Owen {Pterosauria, PI. 19, tigs. 10, 11, 12, 20, 21). 



Figures 10 and 11 of PI. 19 show front (thenal) and back (anconal) views of a mutilated 

 proximal end of the left humerus of this rather small species of Pterodactyle. The 

 reniform articular surface of the head of the humerus (fig. 12, o) is somewhat less extended 

 transversely in proportion to its breadth than in a similarly sized species from the Lias 

 {Pterodact'i/lus Marderi, ib., fig. 9) ; its anconal convex border has a bolder curve. 

 There is no indication of a pneumatic orifice on this surface, as in Birds. The pectoral 

 process {b, figs. 10 and 11) stand out more abruptly from a less extended base (compare 

 with b, figs. 7 and 8, PI. 19). 



The proximal end of the first phalanx of the fourth or wing-finger, which is the 

 subject of figs. 20, 21, 21^ corresponds in size with the portions of humerus above 

 desci-ibed, near which they were discovered. The olecranoid process (ib., fig. 21, c) led 

 observers of the first discovered specimens of this eminently pterosaurian bone to regard 

 it as an ulna. Upon this process is extended part of both the outer and inner concave 

 articular surfaces, so placed as to resemble the two divisions of the ' greater sigmoid 

 cavity ' in the human ulna, the curve and depth of which surfaces is thus augmented, and 

 therewith the security of the flexible joint on which the chief movements of the bat-like 

 vnng take place. The outer surface, shown in fig. 20, is of less extent, in long diameter, 

 than the inner articulation (ib., fig. 21, a) ; a larger proportion of it is supported by the 

 olecranoid process ; and it is better defined along the margin next the longer concavity 

 (a). Nevertheless, the smoothness of the surface of the ridge, dividing the concave 

 articulations, suggests that they combined to fonn a single synovial hinge-joint or 

 ' ginglymus,' limiting the movements of the bones so articulated to one plane, and 

 combining freedom and extent of motion in that plane with great strength of joint. 

 The summit of the olecranoid process in the present specimen shows a rough flattened 

 surface, not a fracture, suggestive of the contact of a sesamoid, probably lodged in the 

 tendon inserted into the phalanx (ib., fig. 2P). 



B.—Pterodadylus PleydelUi, Owen {Pterosauria, Plate 19, figs. 15, 16, 22, 23, 23==). 



The portion of the fossil skeleton of the small species of Kimmeridgian Pterodactyle 

 here figured is the distal half of the left humerus. It shows the generic obliquity and 

 superiority of size of the articular convexity for the head of the radius (ib., fig. 15, a,) ; 

 that for the ulna has suffered fracture, and part of it is lost with the ulnar tuberous ridge ; 



