BETWEEN TYPICAL EEPTILES AND OTHEE ANIMALS. 157 



band, as figured by "Wagler. This is also seen among certain of 

 the Dinosauria, but not among mammals. 



The dorsal rib of a Crocodile is divided on each side into four 

 pieces, of which only the large proximal part is fully ossified. 

 In most mammals the rib consists of two pieces, though a few 

 (as some Dolphins) have one or more of the ribs consisting of 

 three elements. 



In Crocodiles the anterior part of the sternum widens, gives 

 attachment to the pectoral girdle of bones, and is prolonged in 

 front of them. In mammals the general aspect of the sternum 

 is very like that of Crocodiles. The widening and forward pro- 

 longation of the anterior sternal part is quite equalled among 

 true Whales (e. g. JBalcEnoptera); and the Pig, Tapir, Ehino- 

 ceros. Lion, Seal, Thylacinus, for example, present anterior 

 sternal elements similar in form to that of the Crocodile, but 

 which are often compressed like the keel of the bird's sternum, 

 and give attachment usually to the first pair of ribs instead of to 

 the pectoral girdle ; while the bones usually named coracoid and 

 clavicle have but an uncertain existence in most mammals. 



In the Crocodile the scapula unites with another bone usually 

 named the coracoid, to form the glenoid cavity for the humerus 

 to work in. In mammals the humerus usually articulates with 

 the scapula only. In monotremes it articulates with scapula 

 and coracoid ; but then the coracoids uuderlap the episternum, 

 and do not abut against the sternum as in Crocodiles. In the 

 the Mole, among placental mammals, the humerus articulates 

 with a scapula and coracoid, and, as in the Crocodile, that short 

 strong bone abuts against the sternum. 



In shape the coracoid bone in Crocodiles is very like the 

 scapula, but diff"ers from it in being perforated in front of the 

 articulation. Its elongation precludes comparison with mammals ; 

 it is more like the bone in the Echidna than in the Mole. The 

 scapula of the Crocodile, in its elongated flattened form, is not 

 closely paralleled, the Mole and the Ox making the nearest 

 approximations. It is wider from front to back at the humeral 

 end than at the free end, and possesses a prearticular part, which 

 are differences from mammals. In the small development and 

 lateral position of the spine it resembles Echidna. 



The humerus of the Crocodile differs from that of most 

 mammals in not possessing a pit at the distal end for the olecra- 

 non-process of the ulna, and in having a crest at the proximal 



