66 



ANATOMY OF VERTEBRATES. 



54 



more downward, so as to form the body of the rib, which termi- 

 nates, however, in a free point. In the ninth cervical, the rib, ?', 

 is increased in length, but is still what would be termed a ' false ' 

 or l floating rib ' in anthropotomy. 



In the succeeding vertebra the pleurapophysis, fig. 54, k, 



articulates with a hrcmapophysis, and 

 the haemal arch is completed by a 

 haemal spine ; by which completion 

 of the typical segment we distinguish 

 the commencement of the series of 

 dorsal vertebras. With regard to the 

 so-called ' perforation of the transverse 

 process ' this equally exists in the pre- 

 sent vertebra, as in the cervicals ; on 

 the other hand, the cervical vertebras 

 equally show surfaces for the articu- 

 lation of ribs. The typical characters 

 of the segment, due to the completion 

 of both neural and haemal arches, are 

 continued in some species of Crocodilia 

 to the sixteenth, in some (Crocodilus 

 acutus) to the eighteenth vertebra. In 

 the Crocodilus acutus and the Alligator 

 lucius the hremapophysis of the eighth 

 dorsal rib (seventeenth segment from 

 the head) joins that of the antecedent 

 vertebra. The pleurapophyses project 

 freely outward, and become * floating 

 ribs ' in the eighteenth, fig. 55, b, 

 nineteenth, ib. c, and twentieth, ib. d, 

 vertebrae, in which they become rapidly 

 shorter, and in the last appear as mere 

 appendages to the end of the long and 

 broad diapophyses : but the haemapo- 

 physes by no means disappear after 

 the solution of their union with their 

 pleurapophyses ; they are essentially 

 independent elements of the segment, and are accordingly con- 

 tinued, in pairs, fig. 55, 3, 4, 5, 6, 7, and 56, along the ventral sur- 

 face of the abdomen of the Crocodilia, as far as their modified 

 homotypes the pubic bones, ib. 8. They are more or less ossified, 

 and are generally divided into two or three pieces. A short carti- 

 laginous piece, an unossified part of the pleurapophysis, intervenes 



Diagram of anterior vertebras, 

 Crocodile, cc. 



