OUGANIZATION OF THE OBNITHOSAURIA. 103 



membraues, which are well preserved in a specimeu figured by^ 

 Winckler as Pterodactylus Kochii, prove to be exactly in thq 

 same regions as the patagial membraues of the wing of existing 

 birds ; while the great elongation of the wiug-bones in Ornitho- 

 saurs only extends the wing to a similar extent to that in which 

 the wing of a bird is extended by its feathers. It is reasonable 

 therefore to suppose that if less organic energy were directed to 

 formation of the covering for the skin in birds, more might go to 

 the elongation of the wing-bones. 



Finally, in the absence of any manner of evidence as to the 

 existence of winged reptiles, and in face of the evidence as to 

 avian resemblances which has been given, it seems to me hazardous 

 to infer that the characters which some Pterodactyles may seem 

 to have in common with reptiles in the bones which have been 

 discussed, indicate any close genetic relation between the two 

 types. 



The pelvis and hind limb are the least reptilian portions of the 

 Ornithosaui^ian skeleton. Whatever may be the physiological 

 significance of the relation of direction of the ilium to the sacrum 

 in the vertebrate classes, the morphological fact remains that in 

 birds the ilium extends along the sacrum both in front of the 

 acetabulum for the femur and behind it, and that this condition 

 characterizes no other existing group of animals. In mammals 

 and batrachians the ilium is directed forward, while in reptiles it 

 usually directed backward or is vertical. And though the ilium 

 of a seal makes an approximation to the ilium of a crocodile, which 

 may be to some extent functional, these osteological characteristics 

 of classes are sufficiently well marked to suggest the inference 

 that an animal with the avian form of ilium is likely to be related 

 to bii'ds, either as an ancestral or as a parallel group. Like 

 the whole pelvis the ilium is vax'iable among Ornithosaurs ; and in 

 so far as it diverges from the avian form, it approximates to the 

 mammalian shape. But it is rarely, if ever, so deep as in a bird, 

 never has the characteristic avian form, terminates at both ex- 

 tremities in relatively narrow rounded processes, and is attached 

 to sacral ribs which are longer than is usual among birds. There 

 is also a remarkable difference from birds in the ilium joining the 

 pubis and ischium in the middle of the acetabulum, which is thus 

 made imperforate in the specimens which I have examined. This 

 imperforate character is also found in reptiles. And though the 

 ischium and pubis are occasionally directed backward after the 



LINN. JOUBN. — ZOOLOGY, VOL. XUI. 10 



