98 MS. H. G. SEELET OK THE 



Witli tliat character necessarily follows the absence of a furcula, 

 seeing that there is no surface on the coracoid to which it might 

 be attached. 



In the so-called ShampJiorhynchus BucMandi, and apparently in 

 Dimorpliodon, this clavicular process of the coracoid is developed, 

 though perhaps a clavicle may not be inferred for those genera. 

 The scapula is a bone which, in Dimorpliodon, is compressed and 

 curved like the scapula of the fowl, and was similarly placed. 

 In the Oolitic fossils the bone is still more like the scapula of a 

 bird than any thing else ; but in the Cambridge- Greensand genera 

 the form of the bone is svibcylindrical, terminating backward in 

 an expanded and abruptly truncated and ovate end. This is not 

 bird-like, and not like the bone in any other animal. 



The only reptiles which have the pectoral arch sitnilariy consist- 

 ing of scapula and coracoid are crocodiles and chameleons. Since 

 the scapula is elongated in Cliamceleo as well as in the Mole {Talpa}, 

 the eloDgation is evidently not correlated exclusively with develop- 

 ment of the pectoral muscles. And since the coracoid has no corre- 

 sponding form or function in bats, the shape of that bone in Pte- 

 rodactyles cannot be explained by its function only. The Orni- 

 thosaiirian hnmerus, with marked resemblances to birds and 

 chameleons, is yet so different as not to be mistaken for either. 

 Remembering that Ornithosaurs were often quadrupedal, and that 

 the whole fore limb was usually modified for walking as well as for 

 flight, it is scarcely to be expected that the resemblances of limb- 

 bones to those of any existing mammals should be remarkable. 



In the forearm both bones are large and usually of equal size, 

 as Yon Meyer and Professor Owen long since pointed out ; so that 

 the ulna is as large as in a bird, and the radius much larger. The 

 ulna is large in birds, I presume, because the feathers are attached 

 along its shaft, and the equality in size of the bones in Pterodac- 

 tyles may indicate that both bones performed nearly equal amounts 

 of work. Still the resemblances to birds are more marked than 

 to other animals. There is, however, in many species a third 

 bone in the forearm, which is articulated to the pisiform bone. It 

 is imperfectly developed proximally, and appears to correspond 

 to the olecranon seen in the skeleton of Ophthalmosaurus. In 

 Cycnorhamphus a second bone of this kind appears to be present, 

 tlie homology of which is more difficult to understand. 



The carpus has always been regarded as reptilian, seemingly 

 because it consists of two rows of bones. It is a very variable 



