FOSSIL AND RECENT 



71 



soc 



epo 



Fig. 35. Protarpon priscus (Woodward). Neurocranium, dorsal view of the otic 

 region. Based on B.M.N.H. P.356. 



Formation and locality. London Clay (Ypresian) of Sheppey, Kent, England. 



Description. Neurocranium. The skull roof is flat, marked only by two promi- 

 nent ridges, which attain their greatest development at the sphenotic level. The 

 mid-line of the skull roof is slightly depressed, an appearance which is enhanced by 

 the presence of these ridges. A smaller specimen, B.M.N.H. P.356, shows weak 

 ridges. By analogy with Tarpon and Megalops these ridges contained the supra- 

 orbital sensory canals. The supraorbital sensory canal is known to pass posteriorly 

 into the parietal bones in Megalops and Tarpon and a similar situation existed here 

 as evidenced by the pores upon the parietal bones illustrated. In the otic region the 

 roof is parallel-sided, but posteriorly it is produced into three processes ; a median 

 supraoccipital with large epiotic processes on either side. 



Each frontal has a square posterior margin and in consequence imparts an ' L '- 

 shape to the adjacent pterotic. The medially united parietals are slightly longer 

 than broad and have a sinuous suture with both pterotics and frontals. The lateral 

 ethmoid is similar to that of Tarpon. 



In posterior view the pentagonal supraoccipital bears a prominent supraoccipital 

 crest, on either side of which is a slight depression. The epiotic also exhibits a faint 

 depression immediately beneath the epiotic process. This depression is continued 

 upon the exoccipital. The exoccipital is large and meets its fellow of the opposite 

 side above and below the foramen magnum. Laterally the exoccipital forms the 



