SKELETON OE SIRENIA. 



431 



lower ossification in tlie haemal 

 arch establishes a bony * ha^ma- 

 pophysis,' h, and represents the 

 ' ischium.' It is ligamentously 

 connected at its lower end to 

 its fellow, completing by such 

 ^ symphysis ischii' the pelvic 

 hiemal arch. In the vertebra, 

 E, the proximal part only of the 

 pleurapophysis is ossified, as in 

 the lumbar series ; and this is 

 the case with the succeeding 

 vertebrae : but the centrums ex- 

 hibit, at their under surface, arti- 

 culations for parts answering to 

 the loAver portion, h, of the haemal 

 arch of the vertebra D. The 

 parts in question, 9, lo, ii, h, are 

 severally united together by their 

 lower or distal ends, at first liga- 

 mentously, but afterwards by co- 

 ossification, constituting inverted 

 bony arches of the chevron shape, 

 and which are serially homolo- 

 gous with the bony haemapophy- 

 ses, h, of the pelvis, and the 

 sclerous or cartilaginous h^em- 

 apophyses of the trunk : they are 

 dislocated from their pleurapo- 

 physes and approximated to their 

 centrums, with a slight horizontal 

 displacement leading to their 

 partial articulation with that of 

 the vertebra succeeding their 

 own (see fig. 188, p. 299). These 

 haemapophyses, fig. 292, h, Cd, 

 are not developed in the terminal 

 vertebrae, the last six of which 

 are represented by horizontally 

 flattened centrums, o, sustaining, 

 as in Cetacea, a horizontal tail-fin. 

 The ribs of the dorsal verte- 

 bra3, fig. 292, jA, are massive, 



Ungong (Halicore) , 



