2 



BRITISH FOSSILS. 



curvilinear character begins to be appreciable. The reasonni adduced 

 in favour of the new scheme, from the teeth and other structural 

 details, are still more untenable than those derived from the dermal 

 characters ; but the subject is too large to be further pursued in 

 this article. The genus Megalurus is unquestionably a member of 

 the Ganoid order as defined by Agassiz, the scales being invested 

 with a coat of enamel, which, although thin, is unmistakeable. I 

 have ascertained that the scales of Leptolepis are similarly coated, 

 a fact which is disputed by M. Pictet, and other continental 

 ichthyologists. The large teeth of Megalurus designate its 

 position as a genus of the Sauroid family. The structure of the 

 vertebral column and its appendages, with the exception of the 

 caudal portion, resembles that of the corresponding parts in Gaturus. 

 The distal extremity of the column and the caudal fin are most like 

 those parts in Macrosemius and Lepidosteus, with some affinities 

 to the C?elacanthoid family, more especially to the genus Undina 

 of Count MUnster. The genus Oligopleurus of Mr. Thiolliere 

 appears to be intermediate in character between Gaturus and Mega- 

 lurus, and affords an easy transition from the one to the other. 



Description. — All the species of this genus hitherto described 

 are from continental localities, their stratigraphical position being 

 limited to the upper region of the Oolitic system. The subject of 

 this article was discovered last year by Mr. Damon in the vicinity 

 of Weymouth. It is intermediate in size between Megalurus lepi- 

 dotus and Megalurus elongatus of Agassiz ; it differs from the 

 former in having the head comparatively shorter, the body more 

 slender, and the scales more elongated ; and from the latter in being 

 a shorter and deeper fish. The specimen measures six inches from 

 the nose to the extremity of the vertebral column, by one inch and 

 a half in depth from the dorsal to the ventral fins. The body 

 diminishes very slightly to the tail, the smallest diameter being one 

 inch and one tenth. The head is one inch and seven-tenths in 

 length, by one inch and two-tenths in depth. The scapulocoracoid 

 bones are strong and smooth, having a thick prominent rib on 

 the inner anterior margin. The vertebral column traverses the 

 centre of the body. It is straight until it nearly reaches the tail, 

 Avhere it has an upward curvature. It contains about fifty bi- 

 concave vertebrae. The apophyses are short for the proximal two 

 thirds of the column, but in the distal third they increase consecu- 

 tively in length to the base of the caudal fin, and thence decrease 

 towards the extremity of the column. The pectoral and ventral 

 fins are small and indistinct. The first ray of the dorsal fin is imme- 



