98 FOSSIL FISHES OF THE ENGLISH CHALK. 



oral border straight; teeth somewhat smaller, stouter, and less inclined than those 

 of the dentary, minute at the hinder end of the bone. 



Description of Specimens. — The type specimen is very fragmentary, and this 

 species is best known by the associated dentary and maxillary bones, which are 

 figured in the British Museum Catalogue (1901, loc. bit.). The outlines of these 

 two elements are reproduced in the accompanying Text-fig. 24. 



Horizon mid Localities. — Zone of Holaster subglobosus ; Upper Hailing and 

 Dover, Kent; Dorking, Surrey. 



3. Ichthyodectes tenuidens, A. S. Woodward. Plate XXI, fig. 7. 



1901. Ichthyodectes tenuidens, A. S. Woodward, Catal. Foss. Fishes B. M., pt. iv, p. 104, pi. ix, fig. 6. 



Type. — Imperfect skull from zone of Holaster subglobosus ; British Museum. 



Specific Characters. — Jaws closely resembling those of I. elegans, but the teeth, 

 especially those of the maxilla, more slender. 



Description of Specimens. — The type specimen of this species is the only nearly 

 complete head of Ichthyodectes hitherto obtained from the English Chalk. It is 

 exposed in right side-view (PI. XXI, fig. 7) and from above, but the fossil is 

 transversely fractured and slightly distorted at the front border of the orbit. The 

 cranial roof is narrow, exhibiting posteriorly the usual median crest, which is 

 continued forwards along the middle line of the frontal region as far as the com- 

 paratively small ethmoid bone. None of the bones are externally ornamented. 

 The very large size of the eye is indicated by fragments of the ossified sclerotic 

 (scl.) ; immediately behind this are the remains of thin cheek-plates (co.), with 

 traces of the slime-canal, which seems to have had radiating branches; while in 

 front may be observed the robust prefrontal (prf.), with its flattened inferior 

 facette for the palatine, which is displaced {pi.). The maxilla (ma?.) is long and 

 slender, but much fractured, so that its anterior end is displaced, and only three of 

 the slender teeth remain ; a facette postero-superiorly shows the extent of overlap 

 of a supramaxillary bone. The outer surface of the dentary (<].) is smooth and 

 only gently undulating, without any sharp longitudinal ridge. The preoperculum 

 (pop.) is shown to be much expanded, with thickened anterior margin, and the 

 usual radiating branches of the slime-canal. 



Fragments of jaws of larger size, which may belong to this species, are remark- 

 able for the delicate flaky texture of the bone. 



Horizon and Localities. — Zone of Holaster subglobosus •. Burham and Hailing, 

 Kent. 



