324 NOTES ox CENTEINA SALYIANl. 



Stomacli empty. Spleen in two portions, one in front of the stomacli 

 and one in tlie mesentery of tlie large intestine. Pancreas and 

 rectal gland present. 



As in other Elasmobranchs destitute of a nictitating membrane^ 

 the cartilaginous skeleton shows a more or less primitive arrange- 

 ment. The notochord is not continuous through the centra of the 

 vertebral column^ but the column itself is entirely cartilaginous, the 

 centra corresponding with the neural arches. The interneural 

 pieces exactly resemble the neurapophyses inverted, and are inter- 

 posed between them like wedges, the apices reaching the centre as 

 in Acanthias. No pleurapophyses are present. 



The conspicuous spines which support each dorsal fin also mark 

 a certain resemblance to Acanthias. There is, however, a distinct 

 difference in that the spines of the spur-dog pass off from the neural 

 arch of the vertebral column in exactly the same direction as, and 

 are parallel to, the anterior margins of their dorsal fins ; whereas in 

 Centrina the spines run in opposite directions, the anterior one 

 pointing forwards, the posterior one backwards. 



In both cases they correspond, in position and arrangement, to 

 modified neural spines, but in the fleshy fin of Centrina there is no 

 arrangement of supporting cartilaginous plates as seen in the fin of 

 Aca7ithias. 



The position of each spine is suggested in the figure. 



