98 WBALDEN AND PURBECK FOSSIL FISHES. 



the cheek-plates, there are traces of the large postorbitals, ornamented with a few 

 sparse tubercles ; and above them is the characteristic triangular postero-superior 

 circumorbital, similarly ornamented and traversed by the deep groove of the slime- 

 canal with its short posterior branchlets. An antero-superior circumorbital, also 

 apparently of triangular shape, is finely tuberculated ; but a small anterior circum- 

 orbital, traversed by the slime-canal, is smooth. Remains of an ossified sclerotic 

 ling are distinct. 



As shown both by the type specimen and by the original of PI. XX, fig. 2, the 

 hyomandibular (km.) is an expanded lamina strengthened in the middle by a 

 vertical rod-shaped ridge; and there is a small symplectic (sy.) of the Amia-tyipe, 

 widest at the upper end, behind the thin, fan-shaped quadrate (qu.). The ento- 

 pterygoid is covered with a cluster of minute, almost granular teeth. The ecto- 

 ptervgoid seems to have borne very small conical teeth. The long and slender 

 maxilla (771.1?.) is gently curved downwards behind, where it is overlapped by a 

 single small supramaxilla (smx.). Its external face is smooth, and its upper border, 

 just in front of the orbit, rises as usual into a broad laminar process. Its oral 

 border bears a row of small conical teeth, which are smallest ami curved forwards 

 in the hinder portion. The premaxilla (pmx.) seems to have been fused with the 

 base of the rostrum, and its recurved conical teeth diminish in size forwards. The 

 mandible is deep in proportion to its length, and its articulo-angular portion (<<</.) 

 is very short. The dentary (//.) is about three times as deep at its hinder end as 

 at its truncated symphysis. The outer face both of the angular and of the dentary 

 is nearly smooth, only marked by the conspicuous slime-canal, which is defined 

 above by a ridge and fringed below r by a series of short branchlets. The oral 

 border of the dentary bears a single regular series of large, smooth, and stout 

 conical teeth, which are flanked near the symphysis by a short row of compara- 

 tively small conical teeth. Similar small teeth are also seen in the type specimen 

 on the upper edge of the displaced splenial bone. The presymphysial bone (ps.) 

 is imperfect in the type specimen, but well preserved in the original of PI. XX, 

 fig. 2. It is triangular in shape, not much longer than deep, and nearly smooth 

 on its outer face. Its oral border bears a row of smooth conical teeth, which 

 decrease in size forwards. 



The operculum (op.), which must have been about as broad as deep, is nearly 

 smooth, only marked by some sparse minute tubercles. The other opercular bones 

 and the branchiostegal rays have not been well seen, bu,t the preoperculum seems 

 to have had the usual triangular expansion of its lower portion. As already noted 

 by Egerton, the removal of the operculum in the type specimen exposes remains of 

 the slender branchial arches, which bear a widely-spaced series of slender gill- 

 rakers (fig. la). 



The smooth cylindrical vertebral centra are crushed flat in the fossils but seem 

 to have been about as long as deep throughout the whole length of the axis. 



