560 5in. A. SMITH AvooBWARD OX TUE [June 20, 



essential features in the osteology of the group to which it belongs. 

 The exoskeleton is so robust that it is usually well preserved, 

 and the internal bones also exhibit a high degree of ossification. 

 As found in the Oxford Clay of Xorthamptonshire and in the 

 Wealden of Sussex, the remains are in an especially good con- 

 dition ; and the discoveries of ^Messrs. Alfred X. Leeds and Samuel 

 H. Beckles respectively render it possible to obtain information 

 concerning nearly all the more important characters of the skeleton. 

 In the case of one Oxfordian specimen from the Leeds collection 

 in the British 31useum (no. P. 6^41 '), all the bones are isolated as 

 if carefully macerated ; in others the display of the various 

 elements depends upon accidents in fracture. It is the object of 

 the present communication to describe these specimens so far as 

 they add to our knowledge of the cranial osteology of Lej^ndotas ; 

 and finally to compare with the skull of this genus that of the 

 closely related Liassic fish, Dapedius. 



I. Ox THE Craxial, I'acial, axd Opercular Boxes of 

 Lej^jidotus. 



The basicranial axis in Lepidotvs is straight, and the cranium 

 itself is well ossified. The hasioccipital element, known only from a 

 laterally compressed specimen (Plate XLIX. figs. 1 «, 1 h), is highest 

 behind and exhibits on its posterior face a very deep conical fossa 

 for the notochord ( a.f.). Towards the postero-inferior angle of each 

 side there is a small acuminate tubercle or process {x) ; and the 

 inferior aspect of the bone exhibits a broad longitudinal groove, 

 with a flattened rim on each margin, evidently indicatiiig the back- 

 ward extension of the basicranial canal (for the recti muscles of 

 the eye) as far as the occiput. There is some appearance also of 

 one vertebral ring (v.) being fused with the basioccipital on its 

 hinder face. The exoccijjitcd (fig. 1) forms a considerable part of 

 the lateral -wall of the brain-case, and is perforated as usual by a 

 large, transversely oval foramen (/.) for the exit of the vagus nerve. 

 The pro-otic (fig. 2) has a still larger extent than the exoccipital, 

 and exhibits a deep, oblique notch (/.) at its anterior margin for 

 the passage of the fifth nerve. In the interorhdal septum there is 

 as yet no evidence of ossification, and particulars are similarly 

 wanting as to the nature of the pttrotic and opistliotic bones. Of 

 the rostral region it can only be said that the ethmoids are 

 arranged in such a manner that the olfactory nerves must have 

 passed through a pair of long, closed canals, well shown in a 

 Wealden fossil in the British Museum (Plate XLIX. fig. 4, eth.). 



^ This is the tvpe specimen of a new species, Lepidotus latifrons, diagnosed 

 in tJie forthcoming Catal. Foss. Fishes, Brit. SIus. pt. iii. Its principal 

 distinctive characters are: — External head- and opercular bones ornamented 

 with conspicuous tuberculations ; all the teeth with much elevated crowns. 

 Premasilla with six teeth. Each frontal bone twice as long as its maximum 

 breadth : oiicrculum three times as deep as broad. 



