40 FOSSIL FISHES OF THE ENGLISH CHALK. 



observed beneath tlie occiput. The quadrate in the type specimen (fig. 1, qu.) is 

 clearly excavated for the reception of a symplectic (s//.). The stout upper tooth- 

 bearing bone is proved to be the palato-pterygoid arcade by the original of fig. 2, 

 where its hinder end is distinctly continuous with the metapterygoid region ; and 

 part of the latter is again shown in the fragment represented in fig. 6. This fossil 

 comprises the hinder end of a slender ectopterygoid {ecpt.) with characteristic 

 teeth, a fragment of the hyomandibular (lim.), and part of the laminar metaptery- 

 goid (mpt.), which is nearly completely preserved in a smaller specimen (fig. 7). 

 Part of a larger ectopterygoid, with some teeth, is also shown in fig. 5. All these 

 teeth are lanceolate and much laterally compressed, with two sharp, smooth edges, 

 and the outer and inner face ornamented by very delicate vertical striations, which 

 are most conspicuous at the base. The ectopterygoid appears to have extended 

 about half the length of the jaw, overlapping the palatine at the deepest part of 

 the arcade, where it is slightly bent ; though the suture has only been imperfectly 

 observed in one specimen (fig, 3). The palatine is relatively very stout and nearly 

 quadrangular in transverse section, gradually tapering to a point as it slopes down- 

 wards in front. Its flattened inner face (fig. 3, j;Z.) is apposed for a long extent to 

 the slender rostrum; and its hinder end is distinctly shown to be hollow. Its 

 flattened oral face has a sharp outer margin, which deepens behind into a thin 

 bounding wall. It bears two large teeth, of which only the bases, fused with the 

 bone, are indicated in fig. 3, but of which the complete crowns are represented in 

 fig. 4. These teeth are finely striated at the base, but their laterally compressed 

 crowns, each with two sharp edges, are almost or quite smooth. Their relative 

 proportions are noted in the specific diagnosis. Between them there are some- 

 times traces of two or three very small teeth on the outer edge of the bone. The 

 premaxilla and maxilla are relatively very small and delicate, and scarcely known. 

 There are traces of them on the left side of the type specimen (fig. 1 a), where the 

 premaxilla (j^mx.) seems to have been an elongate-triangular lamina of bone, while 

 the underlapped anterior end of the maxilla (mx.) is rod-shaped. The rod-shaped 

 bone represented by fragments outside and below the palato-pterygoid in the 

 original of fig. 3, 7nx., may also perhaps be the maxilla. No teeth are seen on any 

 of these remains. An imperfect mandible in the Willett Collection (no. 88), 

 Brighton Museum, has already been figured by Dixon, oj). cit. The mandible is 

 much fractured on both sides of the type specimen, and its hinder part is lacking 

 in the original of fig. 2. Its principal characters, however, are shown by these 

 fossils. It is gently curved upwards at either end ; its lower portion bends con- 

 siderably inwards ; its hinder end is deepest and sharply truncated just in front of 

 the small articular prominence ; while its symphysial end is bluntly pointed. Its 

 outer face is nearly smooth, only marked by a few longitudinal grooves. The 

 dentary (d.) extends backwards almost to the end of the jaw, covering the articulo- 

 angular {'ig.) so that very little of the latter element is exposed in outer vie^v 



