Mr. J. W. Davis on a new Species of Ptycholepis. 330 
XXX VI.—Deseription of a new Species of Ptycholepis from 
the Lias of Lyme Regis. By James W. Davis, F.G.S. &c. 
[Plate X.] 
Genus PrycHOLEPIs, Agassiz. 
Scales thick, elongated, plicated transversely on the base, 
and deeply turrowed longitudinally ; under surface smooth 
and devoid of rib; pectoral fins pointed; dorsal fin opposite 
the ventral fin; anal fins remote. (Zgerton.) 
Ptycholepis gracilis, sp. nov. 
A well-preserved specimen of Ptycholepis recently came 
into my possession, which differs in several respects from the 
species of this genus which have been described by Prof. 
Agassiz and Sir Philip Egerton. Its form is more attenu- 
ated than that of either of the previously figured species. 
The first representative of the genus, Ptycholepis bollensis*, 
Agassiz, from the Lias at Whitby, was a tolerably large 
specimen about 10°5 inches in length, of which length the 
head occupies more than one fourth. Sir Philip -gerton 
described two species, P. minor T aud P. curtus t; the former, 
from the Lias of Barrow-on-Soar, is a small and elegant fish, 
now in the Enniskillen-Egerton collection at the Natural- 
History Museum, South Kensington. Ptyocholepis curtus is 
a much shorter and thicker fish ; it is 4°75 inches in length, 
the head being 1°75 inch, or more than one third the entire 
length of the fish. The depth of the body at the dorsal fin 
is 1:7 inch. The specimen now before me is 7 inches in 
length from the snout to the termination of the tail; of this 
length the head occupies 1‘5inch, and the depth of the body 
at the dorsal fin is 1°5 inch. In proportion to the size of the 
whole fish the head is much smaller than in any of the species 
before mentioned, and the form of the body is slender and 
graceful as compared with either P. bollensis, Ag., or P. 
curtus, Kg. ‘The anterior portion of the dorsal outline of the 
specimen is slightly broken, the ventral and caudal margins 
are intact, and the lateral surface of the body and head is 
beautifully preserved. 
The head is small, more or less triangular, with a bluntly- 
rounded snout; the posterior outline of the operculum is_ 
* “Poissons Fossiles,’ vol. ii. part 2, p. 108, pl. lix. 4, figs. 1-3 (1883-43). 
+ ‘Memoirs of the Geological Survey,’ dec. vi. pl. vii. 
t Ibid. dec. viii. pl. viii. (1853). 
