Extinct Eel from the English Chalk. 323 



maxilla {m:v.) ; and this element on tlie leftside of the fossil is 

 displaced so as to expose the oral face, which is expanded, 

 slightly concave, and marked with the bases of attachment of 

 clustered small teeth. The premaxillse [pmx.) seem to be 

 fused into a continuous mass with the mesethmoid and vomer. 

 The bone thus formed is expanded and obtusely rounded in 

 front, while its oral face is covered with a dense cluster of 

 small bluntly conical or hemispherical teeth. The mandible 

 (»?(/.) is deepest in the coronoid region and tapers towards 

 the symphysis with a characteristic curvature. The oral face 

 of the dentary bone is somewhat expanded and covered with 

 a cluster of obtuse teeth resembling those of the rostrum but 

 smaller. Attached to the hinder border of the mandibular 

 suspensorium on the right side is the well-preserved pre- 

 operculum [p. op.). This is a rather stout bone, with thick- 

 ened straight anterior margin and a small semicircular 

 posterior expansion. The operculum {op.) is a very small 

 bone, constricted just below its thickened suspensory articula- 

 tion and slightly expanded distally. There are traces of 

 vertebrae, but these are too imperfect for description. 



The osteological characters of the head and opercular appa- 

 ratus from Clayton now described seem to prove conclusively 

 that tiie specimen belongs to a typical generalized eel. The 

 only difficulty arises in connexion with its generic and 

 specific determination. Its close resemblance, however, to 

 the head of Urenchelysj as known from the Upper Cretaceous 

 of Sahel Alma in the Lebanon, suggests that it may best be 

 referred to this genus, while it differs from each of the known 

 species not only in its much larger size, but also in the depth 

 of the head compared with its length. The species from 

 Sahel Alma has a relatively longer, that from Hakel a rela- 

 tively shorter, head. The species from the English Chalk 

 may therefore receive the provisional name of Urenckelys 

 anglicus. 



EXPLANATION OF PLATE IX. Figs. 1, 1 a. 



Fiy. 1. Urenchelys anglieun, sp. n. ; head with opercular apparatus, right 

 and left (1 «) lateral aspects, tiat. size. — Lower Chalk ; Clayton, 

 Sussex. [AN'illett CoUectiou, Brighton Museum.] 



ec, ectopterygoid ; /?•., frontal; ^ni., hyoniandibular; m., mesethmoid; 

 md., mandible ; nu:, maxilla ; op., operculum ; p.op., preoper- 

 culum ; pa., parietal; pvi.v., premax)lla ; j'W., quadrate; sp,, 

 sphenotic (postfrontal). 



21* 



