PHYLOGENY OF THE PAL^EOGNATHyE AND NEOGNATH^E. 211 



Casuarius in having a bony bar running from the diapophysis backwards to the 

 hyperapophysis. 



The thoracic vertebrae call for no special remark here. They have already been 

 minutely and carefully described by Mivart. 



The vertebrae known as the cervico-thoracic should probably be regarded as true 

 thoracic vertebrae, the ribs of which have lost their sternal segments through the 

 backward shifting of the sternum. This view has already been promulgated by the 

 late T. J. Parker. Writing of Apteryx, he says : " The occasional absence of 

 the cervico-thoracic uncinates, taken in connection with the vestigial condition of the 

 ribs in one case and with the fact that in the same skeleton the first thoracic rib 

 of the right side terminates ventrad in a blunt free end and has no sternal portion, 

 seems to point to an inclusion of anterior thoracic vertebras in the cervical region by 

 atrophy of their ribs." 



b. The Synsacral Vertebrce. (PI. XL1V. fig. 5.) 



In Casuarius there are 8 (eight) pre- and 8 (eight) post-sacral vertebrae, with the 

 two true sacrals numbering eighteen synsacrals. 



Of these, two are thoracic. The 1st lumbar has large parapophysial processes ; the 

 2nd to 3rd of this series are much smaller; the 4th and 5th become larger and 

 abut, the 4th against the pectineal process and the 5th against the ischium. Behind 

 these follow two lumbo-sacral. The true sacrals are closely crowded and have slender 

 parapophysial processes, which abut against the ilium and ischium immediately behind 

 the acetabulum. Behind these in C. bicarunculatus lie two pseudo-sacrals with large 

 parapophysial processes abutting against the ilium. But for the sacral plexus they 

 might readily be mistaken for true sacrals. They are really the first two caudals, behind 

 which follow six fused caudals with diminishing and backwardly directed transverse 

 processes. In other Cassowaries there is but one pseudo-sacral. The sacral vertebrae 

 do not bear diapophyses. 



In Dromceus the number of synsacral vertebrae is the same as in Casuarius. The 

 6th lumbar, however, does not send out a parapophysis to abut against the pectineal 

 process. 



The neural spines of the synsacral vertebrae are all highly pneumatic, and made up 

 of loose cancellated tissue. They remain separate for some time after hatching, but 

 in the adult are fused into one mass, all traces of separate vertebrae being lost. In the 

 young bird the pre-sacral vertebrae are just distinguishable between the closely 

 approximated pre-acetabular regions of the ilium. The post-sacral have the neural 

 spines laterally expanded so as to keep the post-acetabular ilium moderately widely 

 separated, so that between each vertebra is a deep loculus (PI. XLIV. fig. 5). 

 In the adult the whole becomes roofed over by a thin bony plate extending across 

 from the post-acetabular ilium of one side to that of the other. 



