2 



BRITISH FOSSILS. 



probably not more than 9 inches in length by 2| inches in depth, 

 and bears undoubted marks of mature age in the successive lines 

 of growth engraven on the surfaces of the scales. The head is 

 imperfect, but»from what remains it seems to have been longer and 

 narrower than in Lepidotus minor. A mutilated dorsal and ventral 

 fin are the only natatory organs preserved. The former is smaller 

 and less powerfully constructed than is usual in the Lepidoti; the 

 fulcral scales are shorter and narrower, and the fin rays more arched 

 than in Lepidotus minor ; the latter is situate rather nearer the 

 head than in that species. The trunk is more slender than in any 

 of the genus, and afi'ords an unmistakeable characteristic of the 

 species ; but in addition to this we find in the scales such clear 

 specific indications, that they could be recognized in the most im- 

 perfect and fragmentary condition. Those on the anterior part of 

 the body are larger in the vertical than in the longitudinal direc- 

 tion ; about the flanks these dimensions are nearly equal ; while in 

 tlie vicinity of the tail the longitudinal diameter is the greatest. 

 They have the upper border convex, and the lower one concave on 

 the greater portion of the body, which gives a remarkable undulat- 

 ing character to the cephalo-caudal series. The dorso-ventral series 

 are more oblique than in Lepidotus minor, and the joinings of the 

 scales in the succeeding columns fall nearer the centres of the scales 

 of each antecedent series. They contain about sixteen scales in 

 each. These are characterized by delicate radiating striations 

 which give a pectinated edge to the posterior margin of the scale. 

 The striations disappear in the caudal region, and the scales are 

 smooth with entire edges. In the young fish the striato-pectinate 

 character seems to have existed to a greater extent than in the adult, 

 as on some of the ca^udal series zigzag lines are still apparent, which 

 at one period must have been the free margins of the scales. 



Affinities. — In the proportion and character of the scales this 

 species approaches the genus Semionotus. 



History. — An unique specimen in the collection of the Earl of 

 Enniskillen. 



Locality. — Lias of Whitby, in Yorkshire. 



Explanation of Plate. 



Fig. 1. Lepidotus pectinatus, size of nature, 

 rig. 2. Scales, magnified. 



P. DE M. Grey Egerton. 



