92 PALEOZOIC FISHES OF NORTH AMERICA. 
This strong and elegant ornamentation differs so much from that of 
any other known fish, that it will serve to identify even the smallest frag- 
ment; but until some other portions of the fish shall be discovered it will 
be impossible to speak positively in regard to its relations. It seems prob- 
able, however, that it was a Crossopterygian Ganoid, having affinities 
with Holoptychius and Onychodus. The cephalic bones of the latter genus 
are covered with somewhat triangular appressed tubercles, which I have 
compared to double cones flattened down on their sides. Some of the 
bones of Sawripteris also exhibit a style of ornamentation closely allied 
to this. 
SPHENOPHORUS LILLEYI, n. sp. 
Plate XX, Fig. 15. 
The very imperfect generic description given above is based on a single 
specimen sent me by Mr. A. T. Lilley, of Le Roy, Bradford County, Pa. 
It was procured from the Chemung rocks in the vicinity, and formed part 
of a large collection of fish remains which he has obtained from the Che- 
mung and Catskill formations. The arrowhead ornamentation is so pecul- 
iar, that it will be immediately recognized wherever seen. It has seemed 
best, therefore, to give a name to the fish it represents, since it is certain 
that it will be hereafter met with by those who are collecting the fossils of 
the Chemung. A more complete description must wait the discovery of 
more material. 
HOLONEMA, nov. gen. 
(Holos, all; nema, thread.) 
A Placoderm fish of medium size, having the body inclosed in armor 
made up of polygonal plates, of which the external surface is entirely cov- 
ered by radiating raised lines of enamel. The central plate of the plastron 
is coffin-shaped, pointed before, broadest near the anterior end, where the 
sides are produced into prominent lateral angles; from this point backwards 
it narrows to a truncated end, which is half as wide as the greatest breadth. 
In the only species yet known this plate is about eight inches in length by 
four inches in breadth. Numerous portions of other plates have been for a 
long time in my collection, but none are sufficiently complete to enable me to 
