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MANUAL OF ZOOLOGY 



neural arches enclose a canal, the neural canal, on the 

 dorsal side of the centra. By the interlocking of certain 

 processes — the articulating processes — of the neural arches 

 the vertebrae in the lizard and rabbit are yet more firmly 

 united together. 



In the dogfish the centra have deeply concave anterior 

 and posterior faces, so that when the vertebra; are in posi- 



A 7"* B 



Fig. 209. — A, three trunk vertebra: of Scyllium from the side; B, a single trunk 

 vertebra viewed from one end; C, three caudal vertebrae from the side; D, a 

 single caudal vertebra from one end. c, centrum; h. a, hsemal arch; u.a, neural 

 arch; ir. pr, transverse process. (After Hasse.) 



tion there are hollows of considerable extent between the 

 centra formed by the apposition of these concave faces. 

 This form of centrum is termed amphiccelous. The entire 

 spinal column is distinguishable into two regions, — the 

 region of the trunk in front and the region of the tail 



