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Bashford Dean Memoria] Volume 



(up), which forms a small process, must 

 probably be regarded as the last frag- 

 ment of the real spine which we find in 

 other Arthrodira. The hind margin of 

 Sp {hm), corresponding with the strong- 

 ly convex front margin, is strongly 

 cohcave. 



On the inside, nearly the whole 

 plate is occupied by overlapping mar- 

 gins. Only Its front part, divided from 

 the hind part by an almost vertical line, 

 is rounded and smooth (fm). The up- 

 per corner was overlapped by AL {al). 

 IL with its thickened hind margin comes 

 in contact with the lower process {il) on 

 the lower margin. Lastly, AVL with 

 its long side process touches the spinal 

 from the inside, fitting into the im- 

 pression on its concave hind margin 

 (avl). Thus the spinal in Dinichthys 

 serves to connect AL, IL and AVL. 



Text-figure 65. 



The spinal plate of Dmichthys drawn: A, from the 



outside; B, from the inside. 



al, part overlapped by AL; avl, part overlapped by AVL. fm, front 

 convex margin; hm, hind concave margin; il, part overlapped by IL; 

 Im, lower margin; Ip, lower process; pr, spine-like process which fits 

 into Ai., iim, upper sigzag margin; u/3, upper process corresponding 

 to the spine in other Arthrodira. 



Text-figure 66. 

 A recon.struction of the relative position between AL, IL and Sf> seen: A, from the side; 



B, from above. 



