1891.] Geology and Paleontology. 657 
16. Length, exclusive of caudal fin, 52 mm.; length of head, 18 
mm. ; do. to base of D. 1 (axial), 21 mm.; do. to base of ventral, 
22mm. ; do. to base of anal, 35 mm.; depth at base of D: 1, 1 
mm. ; do. of caudal peduncle, 10 mm. ; length of tenth dorsal spine, 
8 mm. The specimen measured is one of the smaller ones, and is 
selected on account of its good condition. The larger specimen above 
mentioned measures 34 mm. in depth at the first dorsal spine, and the 
head is 28 mm. in length. 
MIOPLOSUS MULTIDENTATUS, sp. nov.—Represented by a specimen 
nearly perfect, but wanting the caudal and anal fins. It conforms 
exactly to the characters of Mioplosus Cope in the distinct dorsal fins, 
the serrate inferior border of the preoperculum, the two anal rays, and 
the ctenoid scales. Radii: Br. VI (? + ); D. XII-12; V. 6, no well- 
developed spine. Dorsal fins slightly separated at the base; the 
longest spinous ray the third; the first very short. Vertebræ, D. 14, 
C. 16, the last one counted possibly not the last, as its distal end is 
broken off. Scales in about twenty longitudinal rows at the ventral 
fins, and twelve at the caudal peduncle; with proximal radii coarse, 
and no concentric grooves. Posterior limb of preoperculum smooth; 
the inferior with nine robust teeth directed forwards. A serrated crest 
on the posterior part of the skull, which is either the superior branch 
of the posttemporal or immediately adjoins it. Eye large; muzzle 
short, not longer than diameter of orbit. Mouth opening obliquely 
upwards. Ventral fin originating a little in front of dorsal, its rays — 
quite long. Anal originating below anterior ray of second dorsal. 
Depth of body at first dorsal a little less than one-third of length with- 
out caudal fins, and equal to length of head. Length of head, 35 mm. ; 
do. to base of first dorsal, 41 mm.; do. to base of second dorsal, 75 
mm. Length of muzzle to orbit, 11 mm. ; depth of second dorsal, 23 
mm. The proportions ofthis species are about as in the M. abdrevia- 
tus, and the number of scales as in M /abracoides. The peculiarity 
consists in the increased number of spines of the first dorsal fin (nine 
in the other species), and dorsal vertebrae (ten in other species), and 
preopercular teeth (five in other species). 
GeEoLocicaL Posrrion.—The first observation to be made on the 
species above described is that they differ as to species, and three of 
them as to genus, from all others discovered elsewhere, both fossil and 
recent. The next conclusion is that they include no Cretaceous types, 
the only identification with a Cretaceous genus (Sardinius) being 
_ purely provisional. The third point is that the genus Mioplosus has 
been found hitherto in the Green River Eocene only, The age is 
