A FISH BRAIN FROM THE COAL MEASURES 145 
man (’08) has regarded Rhadinichthys as a member of the gan- 
oids with certain teleostean affinities, and has classed it as 
follows: Order—<Actinopterygii, Suborder—Chondrostei (stur- 
geons), Family—Palaeoniscidae. The Coal Measures fish will 
probably find its affinities somewhere in this grouping. 
Since it is probable that the history of these fishes is not gen- 
erally known to the readers of this Journal, it will be well here 
to point out some of the chief facts concerning the geological 
occurrence of the Chondrostei (sturgeons) and give a_ short 
discussion of the characters of the family Palaeoniscidae. 
whe ‘Chondrostei are the oldest and most primitive of the 
Actinopterygii and are first represented in the Lower Devonian 
by a Palaeoniscid genus, Cheirolepis, a contemporary of the 
earliest Crossopterygiil. They occur throughout the Mesozoic 
and continue scantily represented in later periods, to be repre- 
sented by their degenerate descendants of today, the sturgeons 
and paddle fishes. 
The family Palaeoniscidae is characterized by Eastman (’08) 
as: 
Primitive Chondrostei with fusiform bodies, short dorsal and anal 
fins, and usually with a complete investment of articulating rhombic, 
rarely cycloid, ganoid scales. Fulcra generally present at the bases of 
the median fins, and especially along the dorsal border of the upper 
caudal lobe. Ribs are not known to be present. Skull invested by a 
very complete series of paired dermal bones, which in number and 
disposition conform to the normal Teleostome type. The secondary 
upper jaw includes both premaxillae and large maxillae; and, as a rule, 
both the dentary and splenial bones of the lower jaw are dentigerous. 
Except for the absence of an interoperculum, the opercular series of 
bones is complete, including numerous branchiostegal rays. There is 
a single small median jugular plate. 
The above discussion is of interest further in that, in all prob- 
ability, the fish brains from the Coal Measures of Kansas de- 
scribed below belonged to representatives of the Palaeoniscidae. 
There are a few opercular elements preserved in nodules associ- 
ated with the nodules containing the brains, but their associa- 
tion with the same fish is so uncertain that it is best to leave 
the question an open one. 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 25, NO. 2 
