LEPTOLEPIDJE. 
Genus LEPTOLEPIS, Agassiz. 
[ISTeues Jahrb. 1832, p. 14:6.] 
Syn. Ascalabos, G. von Minister, Beitr. Petrefakt. pt. i. 1839, p. 112 
(undefined). 
Tharsis , C. G. Giebel, Fauna d. Yorwelt, Fische, 1848, p. 145. 
Sarginites, 0. G. Costa, Atti Accad. Pontan. vol. v. 1850, p. 285. 
Megastoma, 0. G. Costa, ibid. 1850, p. 287— 
Head large and teeth minute ; sclerotic ossified. Maxilla arched, 
with a slightly convex dentigerous border; mandible prominent, 
and dentary sharply rising into a thickened, obtuse* elevation near 
its anterior extremity ; preoperculum broad mesially, with a large 
inferior limb, marked with radiating ridges ; suboperculum large, 
but smaller than the trapezoidal operculum, from which it is divided 
by an oblique suture. Vertebrae in the form of much-constricted 
cylinders, with little or no secondary ossification. Pelvic fins rela¬ 
tively large ; dorsal fin about as long as deep, opposed to the pelvic 
pair or to the space between the latter and the anal; anal fin small, 
not much extended ; caudal fin deeply forked. Scales completely 
covering the trunk ; no enlarged or thickened ridge-scales. 
The external bones and scales are covered with a very 'thin layer 
of ganoine, always smooth or only feebly rugose. The‘cranial roof 
is flattened in the middle, abruptly truncated behind, and very 
narrow between the orbits the parietals are very small, and the 
suture between the much-elongated frontals is wavy. The para- 
sphenoid is delicate. There is a series of large suborbital bones, 
and the sensor}’ canal traversing them exhibits a number of short 
branches radiating downwards. This is observable both behind and 
in front of the orbit. The sclerotic ring is ossified. The premaxilla 
is small, and the long curved maxilla, having minute teeth on its 
convex oral margin, is contracted, though comparatively robust, at 
its loose anterior articulation. There are also two elongated supra- 
maxillary bones, deeply overlapping the maxilla. The mandible is 
deep in the middle, and consists almost entirely (if not entirely) of 
two elements. The robust dentary bone is remarkable for the deep 
coronoid process rising nearest its anterior end: behind, and partly 
above it, is the large laminar angulo-articular element. The cera- 
tohyal has the ordinary hour-glass form, but is noteworthy for the 
extension of a supplementary delicate straight rod of bone between 
its extremities on the upper side. The opercular apparatus is 
complete, and the sensory canal upon the preoperculum exhibits 
radiating branches resembling those of the suborbital line, The 
branchiostegal rays on the short epihyal are broad and imbricating, 
while those supported by the ceratohyal are spaced and delicate ; 
