736 



MR. C, TATE REGAN ON 



[June 19, 



they may even grow round it and meet laterally, each neural 

 uniting with the corresponding htemal *, 



Text-fie-. 116. 



Diagrammatic transverse sections of vertebrae of CetorJiinus (A), Ginglymostoma (B), 



Galeocerdo (C), Narcine (D), Mmopterus (E), and Squatina (F). (All after 



Hasse.) 

 n, neural arch ; 7i, hajmal arcli; c, calcified double cone; s, secondary calcification ; 



a, principal uncalciiied areas, radiating to the bases of the arches in A, B, 



and C. 



* This extension of the neural and haemal plates round the chordal sheath appeal's 

 to be often inversely proportional to the secondary calcification of the centra. In 

 nearly all the Galeoidei the calcifications extend throughout the centrum and the 

 neural and haemal arches do not extend downwards or upwards, but in Pristiurtis, 

 where the secondary calcification has disappeared, they meet round the centra. 



