546 BRITISH FOSSIL REPTILES. 



metacarpal of the wing-fiiiger. The thenal border of the bone is the thinnest, and is 

 produced at each end into a short |)rocess ; the anconal border of the bone is thicker, 

 especially where it supports the smaller and outer articular metacarpal concavity. 



The proximal surface (ib., fig. 25) is also divided into two principal articulations, 

 but the larger one (c) is subdivided into a concave and a flattened facet. The smaller 

 concave surface (rf) is next the outer and thickest end of the bone. 



The subject of figs. 26 and 27 is the homologous bone, and from the forelimb of the 

 same side, but it shows modifications that plainly bespeak its having come from a distinct 

 species of Pterodactyle. The outer subhemispheric concavity of the proximal surface 

 (ib., fig. 27 d) is relatively larger, as is likewise the flat facet at the inner part of the 

 larger surface (c). The two condylar concavities (« and i) on the distal facet are more 

 equal than in the larger unciforme. 



Both bones exemplify the definite, well-marked, or finished character of the articular 

 surfaces which characterise the l)ones, especially those of the wing, of the volant 

 Reptile. 



I would still be understood to be guided by considerations, not beyond probability, 

 in referring this well-marked bone to the distal row of the carpal series ; for I have not 

 yet had the opportunity of studying a Pterosaurian carpus or tarsus in so well-preserved 

 and undisturbed a condition as would enable me, with certainty, to determine the 

 homologies of its constituent bones. 



§ 4. Pterosauria of the Great Oolite. 



A. — Pterodaclylus Kiddii, Owen {Pterosauria, Plate 19, fig. 17). 



The first phalanx of the wing-tinger (fig. 17), referable to this species is somewhat 

 stouter, but about one eighth shorter, than that bone in the Pterodacfi/las saevicits, 

 Quensted,^ from the Lithographic Slate of Wirtemberg. It indicates a species with a 

 more powerful, though, perhaps, less elongate, wing. The groove for the flexor tendon 

 of the fourth digit, bounded Ijy the prominent thenal extensions of the two articular 

 grooves, is well marked. The extensor process (ib., c) has a relatively longer basis than 

 in the Kimmeridge specimens. A rough groove or Imear depression beginning about an 

 inch beyond the proximal articulation, and extending as far down the fore or thenal 

 surface of the shaft of the bone, indicates the extensive attachment or insertion of that 

 tendon. The shaft is subtriedral, the anconal side being the broadest; it becomes 

 flattened towards the distal end, which expands unequally towards the ulnar side, and 



^ " Ueber Pterodactylas suevicus," 4to, Tubingen, 1855. 



