94 



FOSSIL FISHES OF THE ENGLISH CHALK. 



laminar, vortical crest. The epiotic (epo.) is a long and narrow element, elevated 

 behind into a sharp, longitudinal ridge, which extends backwards as far as the thin 

 supraoccipital crest already mentioned. Its narrow front end articulates with the 



O/IO 



bocc 



Fiu. 22.— Skulls of Chirocentrus dorab, Forsk., upper (A) and left lateral (B) aspects, and Ichthyodedes 

 sp., upper (C) and left Lateral (D) aspects, bocc, basioccipital ; epo., epiotic ; eth., mesethmoid ; fo., 

 fossa in side of otic region ; fr., frontal ; opo., opisthotic ; pa., parietal ; pas., parasphenoid ; prf., 

 prefrontal (ectethmoid) ; pm., pro-otic; ptf., postfrontal (sphenotic); pto., pterotic (including 

 squamosal); socc, supraoccipital; v., vacuities in epiotic- parietal crest ; vo., vomer; I., epiotic- 

 parietal crest ; ii., pterotic crest. 



small parietal bone in a remarkably jagged suture, well seen in PL XIX, fig. 5. 

 The precise forward extent of the parietal (pa.) is not clear, but its probable 

 outline is indicated in Text-figs. 22 c, d. There is no squamosal element 

 separate from the pterotic (pto.), which forms the downwardly and outwardly 



