FOSSIL AND RECENT 25 



there is an elongate pelvic splint bone. The anterior end of this pelvic splint lies 

 free in the somatic musculature. 



Vertebral column. The vertebral column is composed of 68 vertebrae. There 

 are 19 caudal vertebrae. 



Each centrum is amphicoelous and pierced centrally for the passage of the noto- 

 chord. The majority of the centra are as deep as long but those anteriorly are 

 deeper than long while those posteriorly are slightly longer than deep. The centra 

 are marked laterally by fine grooves separated by equally fine ridges. The neural 

 arches, haemal arches and parapophyses are received within shallow pits upon the 

 centra. 



Anteriorly the neural arches are wide and expanded distally. Towards the pos- 

 terior end of the abdominal region the neural arches become more slender and there 

 is no distal expansion. The neural spines of the first 34 vertebrae remain as separate 

 halves but posterior to this level the lateral halves fuse to form solid median spines. 

 The neural spines of the third, fourth and fifth preural centra are somewhat longer 

 and straighter than those immediately in front and aid in the support of the caudal 

 fin-rays. 



The first 47 centra bear parapophyses. To these are attached the pleural ribs. 

 The anterior parapophyses are small but those associated with centra 35-47 gradually 

 increase in length. Behind this level complete haemal arches and spines are seen, 

 the last four being long and stout and involved in the support of the caudal fin-rays. 



Epineural intermuscular bones are only absent from the centrum incorporated 

 into the neurocranium and the last three caudal vertebrae. The epineurals asso- 

 ciated with the first 30 or so vertebrae are attached to the bases of the neural arches. 

 Those behind lie free, the anterior free members having forked bases. Epipleural 

 intermusculars are found throughout the caudal region. All lie free, and like their 

 neural counterparts those found anteriorly show forked bases. 



Sigmoid supraneurals occur between the tips of the first 32 neural spines. The 

 first supraneural is the largest, thereafter they decrease in size posteriorly. It is 

 of interest to note that supraneurals occur between the first few pterygiophores of 

 the dorsal fin. 



Median fins. The dorsal fin lies in the centre of the back and consists of 25 

 fin-rays of which the first four, although paired, are unbranched and not articulated. 

 The seventh ray is both the longest and the first branched of the series. The fin- 

 rays are supported upon 21 pterygiophores of which all except the first two consist 

 of distinct proximal, middle and distal radials. The distal radials lie between the 

 bases of the fin-rays. The first two pterygiophores consist of two radial elements, 

 fusion having occurred between the proximal and middle radial. Together, the first 

 two pterygiophores support the first five fin-rays. 



The origin of the anal fin is midway between the pelvic fin and the caudal peduncle. 

 The anal fin is composed of 17 fin-rays of which the first three are not articulated. 

 The sixth ray is both the longest and the first branched of the series. Thirteen 

 pterygiophores support the fin-rays. The first is long and like its dorsal counterpart 

 consists of fused proximal and median radials and a separate distal radial. The 

 first two pterygiophores support the first six fin-rays. 



