Yol. 69.], SKELETON OF ORNITHODESMUS LATIDENS. 409 



from the place of attachment of the tendon would have a pointed 

 whip-like extremity, by the gradual lessening of the stimulus 

 towards the shoulder. 



The Carpus. 



The general form of the carpais approximates to those from the 

 Cambridge Greensand, and therefore both to Orrdthostomct and to 

 Nyctosaurus ; but, if these two are exactly similar to those of the 

 Cambridge Greensand, then Omithodesmus differs from them in 

 sundry particulars. 



The Metacarpals. 



The length of the wing-metacarpal is intermediate between the 

 long- and the short-tailed forms. In no other Ornithosaur yet dis- 

 covered has the branching-out process on the postaxial border of 

 the proximal articulation, with its separate articulation, been noted. 

 The different figures of the type-specimens seem to show, and the 

 restorations by various authors do exhibit, the small metacarpals 

 parallel one to the other, as in all vertebrates, and not dorsal to the 

 wing-metacarpal. I am convinced that, eventually, it will be 

 proved that the latter was their position in many of the forms 

 restored in the former way. I have found on the distal carpal 

 specimens in the Sedgwick Museum the same articular surface for 

 the small metacarpals as in Omithodesmus Jatidens. 



The Wing-Phalanges. 



The much-reduced dimensions of the third phalange, compared 

 with the second and first, seem to suggest that the shortening of 

 the distal phalange Avas proceeding here, as in the American forms. 

 The second wing-phalange has evidently been reduced in size to 

 the limit of lightness, and the form is best fitted to combiue this 

 with strength. The small rod-like bone (PI. XL, fig. 2, s.b.), 

 which apparently articulated within the semicircular cavity on the 

 proximal end of the first wing-phalange, may be a remnant of 

 the fifth metacarpal. In fact, the wing- digit has been formed by 

 the union of the fourth and fifth phalanges, and the thickening 

 found at both the proximal and the distal ends of the wing- 

 phalanges is the vestige of that union. It is at these extremities 

 that this would be found, if anywhere : for the lessening in size of 

 the bones for reduction in weight would take place in the middle 

 of the shafts, after the anchylosis of the extremities. By this inter- 

 pretation the structure of the manus of the Ornithosaur becomes- 

 simpler. 



The Ischium. 



The separation ventrally of the ischium from the pubis by a deep 

 notch is not found in Dimorphodon, Ornitliostoma, or Nyctosaurus, 

 but agrees with that observed in Pterodactyhis. 



