88 V7EALDEN AND PURBECK FOSSIL FISHES. 



Type Specimen. — Imperfect fish ; British Museum. 



Specific Characters. — As large as the type species, skull attaining a length of 

 about 8 cm. External head-bones ornamented with large flattened tubercles of 

 ganoine. Scales smooth but often marked with a few fine punctations ; hinder 

 border of all the principal abdominal scales delicately serrated. 



Description of Specimen. — The type and only known specimen was discovered 

 by Mr. S. H. Beckles in a waterworn fragment of Wealden ironstone on the beach 

 near Hastings. The fish is curled up, dislocated across the end of the abdominal 

 region, and partly exposed on both sides of the pebble. The remains are shown 

 of the natural size in PL XVIII, figs. 1 — 4. 



The roof of the skull must have been nearly flat, with the postorbital region 

 about two-thirds as long as broad, and the interorbital region much excavated by 

 the relatively large orbits. Of the roof-bones only portions of the parietals (pa,.) 

 and squamosals (sq.) are well seen, these evidently uniting with the frontals in a 

 deeply interdigitating suture. They have a somewhat wrinkled surface, irregularly 

 ornamented with large flattened tubercles of ganoine. The parasphenoid (fig. 2, 

 pas.), seen on the left side of the fossil, extends as far back as the occiput. Its 

 hinder portion is laterally compressed to a sharp median ridge below ; between its 

 lateral wings the lower face widens to bear a small elongate-oval patch of minute 

 teeth ; and further forwards it evidently becomes more expanded. Its lateral wing 

 is relatively large and bifurcated, the anterior limb rising as usual to meet the post- 

 frontal or sphenotic (ptf.), while the posterior limb reaches one of the hinder otic 

 elements. Remains of cheek-plates occur on the right side, ornamented like the 

 bones of the cranial roof with large, irregular, flattened tubercles of ganoine. The 

 postorbitals (po.) must have been relatively large ; and there are small circum- 

 orbitals (co.) above the eye. 



The right hyomandibular (Itm.) occurs in its natural position and shows that 

 the mandibular suspensorium is nearly vertical. This bone is laterally compressed 

 and more expanded above than below, bearing a large and deep prominence for 

 the suspension of the operculum. At least half of its lower end articulates with 

 the symplectic (si/.), which is widest above, then becomes much constricted in its 

 lower half, and thickens again a little at its lower end, which may have articulated 

 with the mandible as in Amia and Cut urns. The quadrate (qu.) and pterygoid 

 bones are thin laminae, only imperfectly shown on the right side of the fossil. 

 'Traces of a patch of small teeth are recognisable below the anterior end of the 

 ectopterygoid. A fragment and a partial impression of the long and slender 

 maxilla (m%.) show a regular series of stout, hollow, conical teeth. The hinder end 

 of the mandible (mil.), with part of the elevated coronoid region, is seen on the 

 right side ; and a splintered fragment of the dentary, with its regular series of stout 

 conical teeth, occurs on the left (fig. 4). 



The opercular apparatus is almost unknown ; but one bone on the right side 



