BRITISH FOSSILS. 



Decade VI. Plate VII. 



PTYCKOLEPIS MINOR. 



[Genus PTYCHOLEPIS. Agassiz. (Sub-luRgdom Yertebrata. Class Pisces. Order 

 Goniolepidoti. Family Sauroidei. Sub-family Sauroidei homocerci. 1st Group. Tail 

 forked.) Scales thick, elongated, plicated transversely on the base, and deeply furrowed 

 longitudinally on the enamel ; under surface smooth, and devoid of rib ; pectoral fins 

 pointed ; dorsal fin opposite the ventral fins ; anal fin remote.] 



Ptycholepis minor^ Egerton. 



Description. — The genus PtychoU'pis has hitherto been restricted 

 to a single species, Ptycholepis Bollensis, remarkable for its occur- 

 rence in several widely-separated localities, viz., Whitby in York- 

 shire, Lyme Kegis in Dorsetshire, and Ohmden, in the kingdom of 

 Wurtemburg. Being in possession of a fine series of specimens 

 from each locality, I am enabled to amend the generic characters 

 formed by Agassiz on imperfect materials. The pectoral fins when 

 perfect are pointed rather than rounded at their extremities, and 

 of moderate size. The dorsal fin is more remote than Agassiz ima- 

 gined, being situate nearly as far back as in Uugnathus, and the 

 anal fin is nearer to the tail tha.n to the ventral fins. A very dis- 

 tinct character obtains in the under surface of the scales, not found 

 in Fugnathus, or the allied genera. In these a projecting rib occurs, 

 traversing the middle of each scale, produced to a point at the upper 

 margin, and recessed at the lower, for the reception of the corre- 

 sponding process of the adjoining scales; but in Ptycholepis the 

 under surface is level, and the articulation is effected by an angular 

 process of the upper margin of the scale, adapted to a notch in 

 the lower margin of the succeeding scale. The specimen under de- 

 scription belongs undoubtedly to this genus, although the small size 

 of the fish and its general outline recal at first sight the features of 

 a Pholidophorus. The total length of the fish, including the tail, is 

 4 inches, of which the head occupies one fourth part ; the greatest 

 depth is 10 lines ; this point occurs immediately behind the gill- 

 covers, from whence the body diminishes gradually to the base of 

 [vi. vii.] 6 H 



