COCCOSTEUS 



131 



pass from the region of hinder plates of the body armour 

 to that of the tip of the tail. This is seen to be bordered 

 by neural and haemal processes, N, H, which in size and 

 character are somewhat comparable with those of Protop- 

 terus or Pleuracanthus. The dorsal fin presents a meta- 

 meral series of supporting cartilages (radial and basal, DR, 

 DB). The basal supports of each pelvic fin have become 

 compressed into a flattened plate, VB. Pelvic fins were 

 present, but there have as yet been found no traces of 

 pectoral appendages. In Dinichthys Newberry believed 

 that a pectoral fin spine was present, and that this fin was 



Pig. 130. — The Devonian Arthrodiran, Coccosteus decipiens,Ag. X 4. Old Red 

 Sandstone, Scotland. (Side view, restored; slightly modified, after SMITH WOOD- 

 WARD.) 



A. Articulation of head with trunk. DB. Cartilaginous basals of dorsal fin. 

 DR. Cartilaginous radials of dorsal fifi. H. Haemal arch and spine. MC. Mu- 

 cous canals. A^. Neural arch and spine, f/. Median unpaired plate of hinder 

 ventral region. VB. Basals of ventral fin. VR. Radials of ventral fin. 



probably Siluroid-like (p. i/i), but this view has not been 

 confirmed. 



The head of Coccosteus was clearly flattened, with 

 orbits and nasal openings near its anterior margin ; it 

 was roofed by a stout buckler of closely fitted dermal 

 plates (Fig. 131), whose outer surface was tuberculate, 

 enamelled, and furrowed by sensory grooves, MC. The 

 arrangement of the dermal plates of Coccosteus was early 

 (1861) compared by Huxley with that of recent Siluroids, 



