294 RECORDS OF THE AUSTRALIAN MUSEUM. 



upon by splints from the adjoining segments that an illustration 

 can only accurately convey the arrangement. 



The accompanying figure shows the thirteenth interneural 

 element, and portions of those in front and behind it. The 

 dorsal spine, apparently corresponding to, the thirteenth inter- 

 neural, is the fourth ; but the twelfth interneural also participates 

 in forming the articular socket. All the other spines, and those 

 of the anal also, similarly arise from two elements. 



The portions of the dorsal and ventral arches in front of their 

 respective spines have their elements rigidly joined, while those 

 posteriorly are loosely articulated ; the same arrangement is seen 

 in the vertebrae, so that lateral motion for purposes of locomotion 

 is permitted ; and in this connection it is to be noticed that the 

 posterior portions of both the arches and the vertebrae are much 

 the stronger. 



The upper and lower arches together form a very regular figure, 

 divided longitudinally by the vertebral column, which, however, 

 lies a little nearer to the dorsal than to the ventral arch. After 

 its union with the skull in front, the upper arch gives off a strong 

 flattened spine, which passing downwards and forwards reaches 

 the occipital bone. The first neural spine is similarly flattened, 

 and strong, and arises apparently from the occipital region of the 

 skull, this portion should therefore be regarded as the first vertebra, 

 though but for the spine its nature would be overlooked; it is 

 anchylosed to the second vertebra by a thin plate of bone above, 

 which encloses the second neural spine, this is thin and styliform ; 

 the second interneural spine is anchylosed to the plate of bone. The 

 neural canal is closed above as far as the middle of the third 

 vertebra, thence is an open canal formed by a thin ridge, the 

 neural process, on each side. 



The first haemal and anterior interhsemals being imperfect, these 

 parts have been restored from Giinther's figure, I cannot therefore 

 describe their arrangement. The first haemal spine arises from 

 the eleventh vertebra, but has a small bony support from the 

 tenth. The ribs, seven in number on each side, commence on the 

 the third vertebra, and are strong and sabrelike. The neura- 

 pophysis and hsemapophysis of the seventeenth vertebra, together 

 with their spines, are directed forwards and broadly flattened to 

 strengthen the attachment with the interneural and haemal arches. 

 These arches are vertically broadened posteriorly, and are received 

 by modifications of the apophyses of the eighteenth vertebra. The 

 nineteenth vertebra is short, circular in section, and the only one 

 permitting rotation. The twentieth is square in section, produced 

 posteriorly above and below to receive the next, which is similar 

 in shape, and the first to actually support the base of the caudal 

 rays. These segments are joined much as is the spliced handle of 

 a cricket bat. The nineteenth to twenty-first form the peduncle. 



