L32 FOSSIL FISHES OF THE ENGLISH CHALK. 



the hinder frontal region, where the bone becomes comparatively smooth. The 

 small, finelv punctate supraoccipital (socc.) is observable at the hinder border of 

 the depression, while quite posteriorly, on the left side, the epiotic (epo.) is crushed 

 outwards. The limits of the parietal (pa.), squamosal (sq.), and frontal (jr.) 

 elements can also be distinguished. The frontals are very large as usual, and 

 exhibit a, longitudinal series of pits along either side of the depression, marking 

 the course of the slime-canal. The terminal mesethmoid (eth.), finely punctate 

 like the supraoccipital, is relatively small and pointed in front, without any 

 expansion. The postorbital cheek-plates (po.), apparently three in number, are 

 large and antero-posteriorly elongated, marked in their hinder portion with slightly 

 radiating furrows, and traversed near the orbital border with the usual slime-canal. 

 There is a long and narrow suborbital plate (so.), slightly excavated at its orbital 

 border, nearly straight-edged below. The antorbital plate (ao.), Avhich is broken 

 by the fracture on the left side, but nearly complete on the right, is remarkably 

 large, deep, and narrow. It is expanded into a triangular plate below, somewhat 

 twisted about an oblique ridge at its middle, and then slightly expanded again at 

 the upper end, where it forms part of the upper border of the orbit, and meets 

 another plate in an oblique suture. The latter plate (x.) forms a small part of the 

 orbital border, and tapers backwards while separating at least the anterior half of 

 the upper postorbital from the edge of the cranial roof. A corresponding plate 

 occurs in the existing Elops (Text-fig. 35, p. 112). 



The premaxilla (pmx.), when viewed from the outer face, is triangular in shape, 

 with a sharp notch in its short posterior border. It meets its fellow of the 

 opposite side in front of the pointed mesethmoid. There are at least 15 tooth- 

 sockets in its marginal series; and one larger tooth can be seen within on the 

 comparatively small palatal extension of the bone. The maxilla (mx.) has 

 a flattened and nearly smooth outer face, bevelled at the oral border, which 

 exhibits many of the relatively small teeth. Throughout its hinder half it is over- 

 lapped by the single supramaxilla (smx.), which is also smooth, tapering in front 

 and ending in a rounded expansion behind. The dentary bone of the mandible (d.) 

 closely resembles that of J', subulidens, but bears only very small teeth. The 

 articulo-angular bone (<i<j.), as usual, is quite short, and the articular facette for 

 the quadrate (qu.) is on its lowest hinder portion. 



Horizon and Locality. — Probably zone of Holaster sulxjlohosm : Hollingbourn, 

 Kent. 



Genus ELOPOPSIS, Heckel. 

 Elopopsis, J. J. Heckel, Denkschr. k. Akad. Wiss., math.-naturw. CI., vol. xi, 1856, p. 251. 



Generic Characters.— -Skull as in Pachyrhizodns. Teeth solid, robust, and 

 Dmcal, usually more or less laterally compressed, and enamelled nearly to the 



