CROCODILIA. 10.5 



Prosencephalic arch (9 presphenoid, 10 orbitosphenoid, 11 frontal, 12 post- 

 frontal) ; 



Rhinencephalic arch (13 vomer, 14 prefrontal, 15 nasal) : 

 and into the heemal arches and their appendages, called 



Maxillary arch (20 palatine, 21 maxillary, 22 premaxillary) and appendages 

 (24 pterygoid, 24' ectopterygoid, 26 malar, 27 squamosal) ; 



Mandibular arch (28 tympanic, 29—32 mandible) ; 



Hyoidean arch (39 epihyal, 40 ceratohyal, 41 basihyal) ; 



Scapular arch (50 suprascapula, 51 scapula, 52 coracoid) and appendages 

 (53—58 bones of fore-limb). 



The bones of the splanchno-skeleton, are 



The petrosal (16) and otosteals (le') ; 



The sclerotals (17) which in most retain their primitive histological condition 

 as fibrous membrane. 



The turbinals (18 and 19) and teeth. 

 The bones of the exo-skeleton, are 



The lacrymals (73). 



The superorbitals (present in Alligator sclerqps). 

 There remains to complete this preliminary sketch of the osteology of the Crocodile 

 a brief notice of the bones composing the diverging appendage of the pelvic arch : 

 these being a repetition of the same element as the appendage of the scapular arch 

 modified and developed for a similar office, manifest a very close resemblance to it. 

 The first bone, called the ' femur,' is longer than the humerus, and, like it, presents an 

 enlargement of both extremities, with a double curvature of the intervening shaft, but 

 the directions are the reverse of those of the humerus, as may be seen in PI. 1, where 

 the upper or proximal half of the femur is concave, and the distal half convex, anteriorly. 

 The head of the femur is compressed from side to side, not from before backwards as 

 in the humerus ; a pyramidal protuberance from the inner surface of its upper fourth 

 represents a ' trochanter ;' the distal end is expanded transversely, and divided at its 

 back part into two condyles. 



The next segment of the hind-limb or ' leg,' includes, like the corresponding 

 segment of the fore-limb called ' fore-arm,' two bones. The largest of these is the 

 ' tibia,' and answers to the radius. It presents a large, triangular head to the femur ; 

 it terminates below by an oblique crescent with a convex surface. 



The ' fibula' is much compressed above ; its shaft is slender and cylindrical, its 

 lower end is enlarged and triangular. 



All these long bones have a narrow medullary cavity. 



The group of small bones which succeed those of the leg, are the tarsals ; they are 

 four in number, and have each a special name. The ' astragalus' articulates with the 

 tibia, and supports the first and part of the second toe. It is figured in Cuvier's 



