EllITISH FOSSILS. 



Decade VI. Plate VI. 



OPHIOPSIS BREVICEPS. 



[Genus OPHTOPSIS. Agassiz. (Sub-kingdom Vertebrata. Class Pisces. Order 



Goniolepidoti. Family Lepidostei. Sub-family Lepidostei homocerci. 2d Group. Body 

 elongated, more or less fusiform.) Scales uniform in size ; caudal fin slightly forked, the 



upper lobe invested v^'ith scales on the superior margin ; pectoral fins long and large ; 



dorsal fin much elongated, and slightly raised ; ventral fins opposite the centre of the 

 dorsal fin ; head small ; opercular apparatus strong and broad.]* 



Ophiopsis breviceps, Egerton. 



Generic Description. — The genus Ophiopsis, as originally defined 

 by Agassiz (Poissons Fossiles, vol. ii. p. 289), was limited to a 

 small number of fishes characterized by an extended dorsal fin, 

 smooth, uniform scales, and a prolonged upper lobe of the dorsal fin. 

 Subsequently, as we find in the " Additions et corrections,'' vol. ii. 

 part 2, p. 289, a fish named Ophiopsis Miinsteri was admitted into 

 the genus, having serrated scales and other features approximating it 

 to the Pholidophori. In consequence of this extension of the generic 

 attributes, the boundary line between Ophiopsis and Pholidophorus 

 becomes very indistinct ; for, while on the one hand we have the 

 elongated form and extended dorsal fin of ^ the typical Ophiopsis 

 procerus occurring in Pholidophorus Flcsheri, on the other we have 

 the small head and serrated scales characteristic of several species of 

 Pholidophorus, cited as distinctive features of Ophiopsis Miinsteri. 

 We find also the uniformity of scales and unequal tail of Ophiopsis re- 

 presented in Pholidophorus latimanus, tenuiserratus, longiserrcdus, 

 and other species of the Oolitic epoch. This is not a fitting oppor- 

 tunity for entering on the general question of the propriety of re- 

 arranging the various forms now included in the genus Pholido- 

 phorus ; as bearing, however, on the subject of the present article, 

 I may hazard the opinion that if any reliance is to be placed on the 

 generic characters assigned by Agassiz to 0p)hiopsi8, it must be on 

 the distinctive features of the dorsal fin ; and if so, all the Pholido- 

 phori having extended dorsal fins must be removed from the latter 



* Agassiz, Poiss. Poss., vol. ii. part 2, p. 289. 

 [VI. vi.] 6 G 



