100 BRITISH FOSSIL REPTILES. 



larynx. The long bony ' ccratohyal' (fig. 13, 40), and the commonly cartilaginous 

 'cpihyal' (ib. 39), are suspended by the hgamentous ' stylohyal' to the paroccipital 

 process ; the whole arch having, like the mandibular one, retrograded from the con- 

 nexion it presents in fishes. 



This retrogradation is still more considerable in the succeeding hsemal arch. In 

 comparing the occipital segment of the crocodile's skeleton with that of the fish, the chief 

 modification that distinguishes that segment in the crocodile is the apparent absence 

 of its hsemal arch. We recognise, however, the special homologues of the constituents 

 of that arch of the fishes' skeleton in the bones 51 and 52 of the crocodile's skeleton (fig. 

 13) ; but the upper or suprascapular piece (50) retains, in connexion with the loss of its 

 proximal or cranial articvilations, its cartilaginous state : the scapula (51) is ossified, as is 

 likewise the coracoid (52), the lower end of which is separated from its fellow by the 

 interposition of a median, symmetrical, partially ossified piece called ' epistefnum' 

 (Hi). The power of recognising the special homologies of 50, 51, and 52 in the 

 crocodile, with the similarly numbered constituents of the same arch in fishes*, though 

 masked, not only by modifications of form and proportion, but even of very substance, 

 as in the case of 50, depends upon the circumstance of these bones constituting the 

 same essential element of the archetypal skeleton; for although in the present instance 

 there is superadded to the adaptive modifications above cited, the rarer one of altered 

 connexions, Cuvier does not hesitate to give the same names, ' suprascapulaire ' to 50 

 and 'scapulaire' to 51, in both fish and crocodile: but he did not perceive or admit 

 that the narrower relations of special homology were a result of, and necessarily 

 included in, the wider law of general homology. According to the latter, we discern 

 in 50 and 51 a teleologically compound ' pleurapophysis,' in 52 a ' hsemapophysis,' and 

 in hs the ' haemal spine,' completing the haemal arch. 



The general relations of the scapulo-coracoid arch to a haemal or costal one was 

 early recognised by Oken. This philosopher, having observed the free cervical ribs in 

 a specimen of the Lacerfa apoda, Pallas {Fseudojjus), deemed them representatives of the 

 scapula, and this bone to be, in other animals, the coalesced homologues of the cervical 

 pleurapophyses.f In no animal are the conditions for testing this question so favor- 

 able and obvious as in the crocodiles and ga vials (PI. 1) ; not only do cervical ribs 

 coexist with the scapulo-coracoid arch, but they are of unusual length, and are 

 developed from the atlas as well as from each succeeding cervical vertebra : we can 

 also trace them beyond the thorax to the sacrum, and throughout a great part of the 

 caudal region, as the sutures of the apparently long transverse processes of the 



* See fig. 5, p. 18, and pi. ii, fig. 2, in ' The Arclietype and Homologies of the Vertebrate Skeleton.' 



t " Auch die Scapula nicht ein Kuoehen, soudern wenigstens eine aus fiinf Halsrippen zusaminengeflossene 

 Platte iii"— Programmiiher die Bedeutuny der Schiidelhwchen, Aio, 180", p. 16. He reproduces the 

 same idea of the general homology of the scapula in the ' Lehrbuch der Natiir-philosophie,^ 1843, p. 331, 

 ^2381. Cams also regards the scapulo-coracoid arch as the reunion of several (at least three) proto- 

 vertebral arches of the trunk-segments. {Urtheilen des Knochen wid Schalen r/enistes, fol., 1828.) 



