102 ME. H. Q. SEELET ON THE 



meleon, there looks to be an a ^n'on probability tbat the number 

 of phalanges, digit for digit, is identical with that in the digits of 

 of the Ornithosaurian hand. Von Meyer appears to have sus- 

 pected a fallacy in this conclusion ; for, in his ' Fauna der Vorwelt,' 

 he observes, " even Cuvier believed that the wing-finger corre- 

 sponded to the fourth finger of lizards ; but lizards, like crocodiles, 

 have five fingers, so there can be no real affinity." In this is a 

 suggestion of explanation of the difficulty. If the animal were 

 essentially a lizard, then it would be improbable that the lizard plan 

 of the hand would be departed from, even when modified for flight. 

 But if the animal is not a lizard, or even a modified lizard, then 

 there can be no h priori reason for anticipating any structure of 

 hand whatever. For though mammals usually have three pha- 

 langes in each digit, Cetacea are not to be classified by digital 

 rules. If the Ornithosauria are admitted to be an extinct order 

 either of reptile or bird type, then, bearing in mind the variation in 

 the number of phalanges of the digits in existing reptile orders, 

 I cannot realize any insuperable difficulty to believing that the 

 phalanges of the second to fifth digits of chameleon, 3, 4, 4, 3, 

 might under exceptional functional conditions become altered to 

 the Ornithosaurian formula 4, 4, 3, 2. The matter of a pha- 

 lange more or less in a digit in an extinct type is not the sort of 

 evidence on which to settle an animal's place in nature, or on 

 which to determine such homologies as those in question. The 

 carpus is the only key to the structure of the hand. If that has 

 been correctly interpreted in the Cambridge-Greensand Ornitho- 

 cheirus, then the inferences which it enforces must, I consider, be 

 true also for the other genera of Pterodactyles, no matter what 

 the number of bones may be in their digits. In short, this portion 

 of the skeleton diverges wider than any other from the bird and 

 reptile types, and is distinctive of Ornithosaurs. 



Thus, reviewing the morphological indications of the fore limb, 

 and of its scapular arch, I fail to detect any characters which can 

 be shown to be decidedly reptilian ; nor do I detect, except in the 

 ways pointed out, any remarkable divergence from birds ; though 

 the divergences are usually sufficient to prevent an experienced 

 anatomist from mistaking even isolated Pterodactyle bones for the 

 bones of birds. On the other hand, the whole limb in every part 

 shows characters which are only found in the bones of birds, which 

 I cannot see my way to explain as adaptive modifications, because 

 bats, which similarly fly, have no such characters. The patagial 



