2 



BBITISH FOSSILS. 



cess. These are covered by the antecedent scales, and mark the 

 periodical increment. I have failed to find these evidences retained 

 in any other species of this genus, although they are permanent in 

 Palceoniscus, and some other genera. The exposed portions of the 

 scales are traversed by alternate longitudinal plaits and striations, 

 radiating at various angles, and increasing in size as they approach 

 the free margins of the scales. These are slightly thickened, and 

 distinctly serrated. The number of teeth carried by each scale is 

 dependent on the number of striae, and these decrease in the more 

 distant parts of the body. The ventral scales are characterized by 

 the coarseness of the cusps, and the paucity of the striae. The dor- 

 sal and ventral fins are as yet unknown ; judging from the frag- 

 ments preserved in the specimens figured, they probably resembled 

 these organs in the other species from the lias. 



History. — The specimens from which the description is taken are 

 in my own cabinet. 



Locality, — Lias of Lyme Kegis. 



Explanation of Plate. 



Fig. 1. The fish, natural size, 

 rig. 2. Same (young). 

 Fig. 3. Scales, magnified. 



P. DE M. Grey Egerton. 



