EGERTON ON FOSSIL FISH FROM THE OXFORD CLAY. 231 



to show that this Lepidotus of the Oxford clay is not referable to 

 any of those species already described by Professor Agassiz. 



Sauroid Family. 



Leptolepis macrophthalmns, Eg. 



Lord Northampton possesses a specimen, nearly perfect, from 

 the same locality as the preceding, referable to the Sauroid genus 

 Leptolepis. It differs from the other numerous species of this 

 genus in the long, slender, and superlatively elegant form of the 

 body, as also by the large size of the orbit. The length of this 

 fish is 5^- inches, depth at the dorsal fin -^ of an inch. The head 

 is small, and its constituent bones thin and smooth. The mouth 

 also is very small, and opens upwards ; the orbit very large in 

 proportion to the size of the head. The spinal column is composed 

 of about 40 vertebrae, the terminal ones decreasing rapidly in size, 

 and tending upwards : the ribs and vertebral spines are slender. 

 The pectoral fins are composed of ten or twelve rays each ; of these 

 the anterior ones are strong. The ventral fins are comparatively 

 large ; they are situate nearly in the centre of the body, and have 

 twelve rays in each. The dorsal fin is small, and immediately oppo- 

 site the ventrals. The number of rays in this fin is not discernible. 

 The anal fin is also small, and situate about half way between the 

 ventral and caudal fins ; the latter organ is symmetrical : the upper 

 lobe has eight rays springing from the terminal vertebra, and has 

 three or four fulcral rays on its upper margin. The lower lobe has 

 from eight to ten rays. The scales are small and thin, finely sculp- 

 tured with concentric striae, as in Leptolepis dubius, and other species 

 of this genus. This fish appears not uncommon in the Christian 

 Malford deposit, as I have seen several specimens in the collec- 

 tions of Lord Northampton and Mr. Pratt, to whose liberality I am 

 indebted for the specimens in my own cabinet. The latter gentle- 

 man has also presented me with two specimens which appear to 

 constitute another species ; they are not, however, sufficiently per- 

 fect to enable me to separate them definitively from the species 

 already described, and the most striking differences appear to be, the 

 greater size of the fish, and the stronger proportions of the ribs. 

 The opercular bones are large, and the pre-operculum is sculp- 

 tured with shallow radiating grooves. The fins are indistinct or 

 wanting in these specimens ; and the scales are wholly absent. I 

 designate this fish by the provisional appellation of Leptolepis 

 costalis. 



Aspidorhynchus euodus, Eg. 



The evidence of the occurrence of this remarkable genus, asso- 

 ciated with the forms described above, con- 

 sists of a few detached scales, and two frag- 

 ments of jaw, one belonging to Lord North- 

 ampton, and the other to Lord Enniskillen. 

 The scales present the peculiar characters 

 found in the other species of the genus, and 

 q 4 



