Genus of Fossil Fishes from the Lias. 449 
pectoral fins large and broad; ventral fin smaller; anal fin 
largest; caudal fin equilobate heterocereal. Notochord 
persistent. 
Lissolepis serratus, Davis. 
The specimen of fossil fish which forms the subject of the 
observations following, presents several peculiar features which 
render it worthy of careful study. For the most part it is 
beautifully preserved, the only part wanting being the pos- 
terior portion of the dorsal margin of the body along with the 
dorsal fin. The bones of the head to a large extent, the 
scales, the pectoral, ventral, anal, and caudal fins remain un- 
disturbed. The entire length between the snout and the 
extremity of the caudal fin is 8-2 inches; of this length the 
head occupies 2°6 inches, or about one third the entire length, 
The greatest depth is between the ventral fin and the dorsal 
surface, where it is 2°2 inches. ‘The cranial bones are strong, 
covered with enamel, the surface of which is ornamented 
with numerous pustulations, somewhat irregular in form. 
The superior portion of the orbit is well defined and pro- 
minent. ‘The orbit is comparatively small, placed about 
equidistant between the upper jaw and the roof of the cranium, 
and ‘7 inch behind the snout. The jaws are large, capable 
of wide expansion, and armed with closely-set, sharp, conical 
teeth, curved slightly inwards, their points capped with 
enamel. The mandible is 1°6 inch in length; it is slightly 
expanded in front near the symphysis ; its median portion is 
somewhat attenuated, whilst posteriorly the bone becomes 
deeper and stronger. ‘The maxilla is large; its posterior 
portion has been slightly displaced and damaged, and is 
consequently obscure ; but it appears to have had a tolerably 
wide expansion towards the orbit. ‘Che premaxillary bone 
is ‘3 inch in length, and has attached to it a number of teeth 
similar to those on the maxilla and mandible. The operculum 
is more or less rounded, except on the anterior margin, 
which presents a concave outline ; attached to its lower surface 
there is an interopercular bone; it is about one half the size 
of the operculum, and probably extends to form a connexion 
with the branchiostegal rays, of which there are some indica- 
tions below the mandible. A series of clavicular bones extend 
posteriorly behind the opercula. The lower portion of the 
external covering of the head is removed, and the scapula, 
contiguous to the pectoral fin, is exhibited. ‘The operculum is 
enamelled and covered with punctures; tiie interoperculum 
presents similar characters. The frontal and ethmoid bones 
do not project beyond the premaxillaries ; they are strongly 
