3<D WATSON & DAY, Notes on some Palaeozoic Fishes. 



the basis cranii. At the back, on each side of the foramen 

 magnum, it is vertically grooved and pierced by three 

 foramina, the hindermost of which is really only a notch 

 whose upper and posterior border is formed by the lower 



A. 



Text-fig. 8. — Diagrams of the dorsal surface of the head of : — 

 A., Diplents valencienvesi, (No. L. 8447.) Achanarras Quarry, 

 Caithness. (Stromness Beds) ; B., Dipterus plaf.ycephalus, (No. 

 L. 10359 ) Thurso East shore. (Thurso Beds) ; C. , Pcntlandia macrop- 

 ferus, (No. L. 10905) Newark, Orkney. (Deerness Beds) ; D., Scau- 



end of a crescent shaped bone which overlies the spinal 

 cord and is unconnected with the brain case below. It 

 is in fact obviously the neural arch of a vertebral segment 

 incompletely fused with the back of the skull. It seems 



