1872.] 339 [Cope. 
The species are distinguished as follows : 
Premaxillary teeth five ; second most prominent ; max- 
illary not concave ; dentary with 80 teeth and bi-convex 
alveolar border, with obtuse extremity............... aoe I. anaides. 
Premaxillaries (?); maxillary straight, large, with 40 
teeth ; dentary straight, not produced at end; teeth 26.... I. etenodon. 
Premaxillaries five; first most prominent; maxillary, 
narrow concave; teeth small; dentary with a hook at 
APOX$ GEOG B0..oy ine ee rep ae eo) ecren oe esate ates ecote I. hamatus. 
Premaxillaries seven ; first most prominent, compressed ; 
BMAL CE occas tet ok ee i NG ees ei ster ee 9 Pe ese eee I. prognathus. 
Premaxillaries twelve ; second most prominent, the bone 
thuch narrowed above-;- SMaller. ..... cis cts ee eee ete I. multidentatus. 
The English species of this genus is figured by Dixon in the Geology of 
Sussex, pl. xxxii.*, figs. 9 and 9*. I can find no letter-press or name re- 
lating to it, and cannot determine its specific characters from the frag- 
mentary character of the piece of mandible figure. 
ICHTHYODECTES ANAIDES. Cope. sp. noy. 
Indicated by two individuals, one with both dentary bones and teeth, 
with vertebrae, the other with many portions of cranium, fin rays, verte- 
bre, and other elements more or less separated. The latter were all taken 
from the upper face of a spur of a limestone bluff, elevated about five 
feet from the ground level, where they were denuded and exposed as on a 
table, prepared for the use of the geologist. 
It is the largest species of the genus, and the anterior premaxillary 
teeth are larger than the posterior. The premavillaries are oblique ovoids, 
very convex on the external face, thinning laterally and above. The 
superior margin presents a thickening, bearing an articular surface, while 
behind it is an open gutter-like inflexion. The large teeth are quite 
cylindrical. Both these bones are preserved. But part of the right maa- 
illary remains. It is thickened above in front of the condyle and is regu- 
larly convex at that point. The teeth are small, there being 10.5 in an 
inch. The margin is not concave. 
The mandibular rami are preserved almost entire. They are short and 
deep, and haye a short angular process, which is relatively shorter than in 
Portheus. The margin rises steeply to the dentary, which presents a 
narrowed rectangle behind. The alveolar margin has two convexities 
with a depression between ; the symphyseal angle is not prominent. The 
lower posterior angle of the dentary is quite prominent for muscular in- 
sertion. The crowns of the teeth are cylindric, slightly curved inwards. 
The dentary bones of the second specimen coincide with these in all 
respects. 
Thirty-three vertebra are preserved, all deeply two-grooved on the sides. 
The ribs are articulated by a sigmoid surface to a broad short element of 
a sigmoid form which is inserted in the lateral groove of the inferior face, 
or articulated by gomphosis. 
