452 Ona new Genus of Fossil Fishes from the Lias. 
and Thrissops, having the dorsal fin situated in the middle of 
the back and the anal fin extended backwards, as in the latter 
genus. The specimen was in the collection of Lord Ennis- 
killen, and is now at the museum in Cromwell Road. It is 
from the Lias at Lyme Regis, and was named 7. Colet. 
The specimen has since been figured and fully described by 
Sir P. Egerton in the ‘ Decades’ of the Geological Survey 
(decade ix. pl. u.).. The dorsal fin corresponds in position to 
those of Oxygnathus. ‘The scales are comparatively small, 
more or less rhomboidal in form, ornamented by raised ridges, 
and with a smooth posterior outline, in this respect differing 
from the specimen now under description. The anal fin is 
remarkably extended, measuring 1°75 inch along the base 
and containing fifty or sixty rays. 
The genus Cosmolepis was established by Agassiz in MS. 
for a single specimen in Lord Enniskillen’s collection from the 
Lias of Barrow-on-Soar. ‘The scales resemble those of Thris- 
sonotus, except that they are smaller in proportion to the size 
of the fish, there being about sixty in a dorso-ventral row, 
and their surface is more thickly ornamented by raised lines 
of the enamel. The anal fin is extended, though not so far as 
in Thrissonotus. ‘The fin-rays are divided transversely into 
numerous ossicles. ‘The genus is fully described by Egerton 
in decade 1x. pl.i. of the Geological Survey. - 
The third genus of the Paleoniscide of ‘Traquair occurring 
in the Liassic formation is Oxygnathus, described and illus- 
trated by Sir P. Egerton in the eighth decade of the Geolo- 
gical Survey, pl. ix. Itis a long and gracefully slender fish, 
with numerous small scales ornamented with oblique ridges 
similar to those of the two genera previously mentioned. 
The jaws are furnished with numerous small incurved teeth 
intermixed with larger ones. ‘The most characteristic feature 
rests in the form of the tail, which is deeply cleft into two 
lobes, the upper one measuring 3°5 inches in length, the lower 
one only 2°5, the fish measuring 11 inches from the snout to 
the fork of the tail. The upper lobe ‘has a scaly invest- 
ment from the base to the extremity, below which issues a 
fringe of innumerable fine rays, with frequent transverse 
articulations and longitudinal bifurcations: the lower lobe 
contains about twenty-four rays ; of these the strongest occupy 
the middle of the lobe, those of the upper and lower margins 
becoming gradually finer as they recede from the centre” (see 
supplement to decade vui.). The teeth of the genus Centro- 
lepis, EXxgerton (decade ix. pl. v.) are similar to those of Oxy- 
gnathus. 'The scales are very thick, their exposed surface 
covered with coarse rug, arranged, not as in the other genera 
mentioned, in a longitudinal direction, but transversely. 
