ON THE VERTEBRATE SKELETON. 187 



a diverging appendage, such as the humerus essentially is, whenever it has an 

 independent existence. By some ichthyotomists, the bone which I call cora- 

 coid (52) has received the special name of ' ccenosteon.' 



Cuvier's usual judgement and acumen seem to have been in abeyance, 

 when, having determined the rays of the pectoral fin to represent the bones 

 of the hand, and the two bones which support them in fishes to be those of 

 the fore-arm, he concluded that, therefore, the great bone which completed 

 the scapular arch "repondra done necessairement a l'humerus." — Hist, des 

 Poissons, 4to. i. p. 274. The great anatomist assigns no other reason : but 

 the arch supporting the ventral fin does not necessarily answer to the tibia 

 or the femur, because neither of these segments are interposed between the 

 arch and its appendage — the modified foot*. The scapula of many reptiles, 

 especially of the batrachia, is manifestly, he proceeds to state, composed of 

 two bones. But in those reptiles the arch is completed below by a third 

 bone, which neither Cuvier nor any other anatomist has called ' humerus.' 

 Now Cuvier's 'humerale' in fishes precisely answers to that third bone in 

 reptiles which he rightly calls the 'coracoid' in that class. 



The coracoid of fishes being thus determined, it necessarily follows that 

 that inconstant bone, or pair of bones (53) posterior to it on each side, cannot 

 be, as Cuvier, Geoffroy, Meckel and Agassiz have supposed, the representa- 

 tive of the ' os coraco'idien' of the reptile and bird. It holds, indeed, as they 

 have said, the same relative position to the bone 52, here called coracoid, 

 which the coracoid in the lizard and bird holds to the clavicle in those ani- 

 mals. But is no account to be taken of the remarkably though normally ad- 

 vanced position of the scapulo-coracoid arch in fishes? Granting, as I shall 

 give evidence to prove in treating of the general homologies of the bones, 

 that the bone (ss) called by Cuvier 'coraco'idien' in fishes appertains to a 

 vertebral segment posterior to the occipital one, yet in the extraordinary back- 

 ward displacement which the true scapulo-coracoid arch undergoes in the 

 air-breathing vertebrates, may not its relative position to that arch become 

 reversed, and the part which is behind in fishes become before in birds ? I 

 entertain no unmeet confidence in the correctness of my view of the special 

 homology of Cuvier's ' os coraco'idien ' in fishes with the furculum or ' clavicle' 

 of air-breathing vertebrates : the argument against such a view, from its pos- 

 terior position in fishes, has not, however, the same weight with me as it ap- 

 pears to have had with Cuvier and his followers : and, leaving this as one of 

 the undecided points in special homology, with the proposition of the pro- 

 visional name of ' epicoracoid' (epicoracoideum, Lat.) for the bone in ques- 

 tion, I proceed to consider other mooted points of special homology, of which 

 there are better and surer grounds for the determination. 



The first discrepancy, demanding special consideration, which meets the 

 eye in the Table I. is that which relates to the determination of no. 6. The 

 German authorities regard what I believe to be the homologue of the human 

 ' ala major sphenoidalis' in the cold-blooded Vertebrata, to be the homologue 

 of the 'pars petrosa ossis temporis.' Cuvier recognises the 'grande aile du 

 sphenoide' in mammals, birds and fishes, but regards my 'alisphenoid' in 

 reptiles as the ' rocher' or ' pars petrosa.' Geoffroy concurs with Cuvier and 

 the German anatomists so far as to view my 'alisphenoid' in the Crocodile 

 as a dismemberment of the petrosal, calling it ' prerupeal ;' but he recognises, 

 like Agassiz and Cuvier, the true alisphenoid in fishes, and with them differs 

 in that respect from the German homologists, It does not appear that the 

 alisphenoid has been mistaken for any other bone than the petrosal, and the 



* The great Linnaeus indicates his appreciation of the homology of the ventral fins of 

 fishes by styling the fishes without those fins ' Apodal.' 



o 2 



