FOSSIL FISHES. 69 
The size and number of the spiny scales of the dorsal line vary much 
in the different species of Jschypterus, and it is not quite certain how far 
these scales can be accepted as a generic character. For example, in some 
specimens of J. tenuiceps, Ag. sp, the scales of the dorsal line immediately 
back of the head are enormously developed, being more than half an inch 
long, erect, radiate, and club-shaped, forming a salient crest, which gives a 
very striking aspect to the fish. On the other hand, in J. /atus J. H. R. the 
anterior scales of the dorsal line are oval and not spined, while the scales 
back of these, though spined, are generally depressed and inconspicuous. 
In the figure of Paleoniscus altus published by Mr. Kirkby! the form 
is almost exactly that of the specimens of Jschypterus latus from Plainfield, 
N. J., and the size is but little less. The head bones, scales, and fins seem 
to be quite the same, only no spined scales appear in Mr, Kirkby’s figures 
and descriptions. If this should be made a generic character, these two so- 
closely allied little fishes must be separated, but if the differences noticed 
above between P. fenuiceps and P. latus should be found to exist in equal or 
greater degree among other species, they should be given only specific value, 
The disparity in form between Paleoniscus altus Kirkby and P. varians 
Kirkby would seem to be associated with some other characters which sug- 
gest a generic distinctness; for example, the operculum is large and rounded 
in the latter, narrow and crescent-shaped in the former. That P. altus and 
P. glaphyrus are members of the same genus can hardly be doubted; but 
whether P. varians and P. Ablsii should be united with them may perhaps 
be questioned. The form of the body is certainly very different, and in P. 
altus the operculum is semilunar and the branchiostegals are scarcely visible 
(characters common to Jschypterus), while in P. varians and P. Abbsii the 
opercula, including subopercula, are nearly round and the branchiostegals 
are very conspicuous. 
ACENTROPHORUS CHICOPENSIS, Ni. Sp. 
Pl. XIX, Figs, 3, 4. 
Fishes six inches long by one and three-eighths inches wide, ereatest 
breadth near head, from which point the body slopes equally above and 
= 
1Loe. cit. 
