SOME NEW POINTS IN DINICHTHYID 
OSTEOLOGY. 
C. R. EASTMAN. 
Tue standard of comparison for all Arthrodiran fishes is the 
typical genus Coccosteus Agassiz, the osteology of which is 
known in the minutest detail. As our knowledge of allied 
genera increases, the more closely do we find them connected 
by intermediate stages, and the better are we able to trace the 
sequence of modifications passed through by them. The group 
of Dinichthyids (Dinichthyine) is a large one, and contains 
many bizarre forms, most of which are still very imperfectly 
known. But when their characters shall have been fully 
investigated, the wide range of variation manifested by them 
will be found reducible to order, and the whole promises to 
constitute one of the most interesting evolutionary series 
known among fossil fishes. 
The characters of Dinichthys have been made out very gradu- 
ally, through slow, persistent effort, but we are still far from 
having a complete knowledge of any one species. The only 
one in which the cranial osteology has been worked out with 
tolerable accuracy is D. intermedius, although the heads of 
D. terrelli and several smaller forms are not uncommon and 
are not always ill-preserved. Tardiness in acquiring informa- 
tion was inevitable, however, in the case of the Ohio Dinich- 
thyids, owing to their prevailing mode of occurrence in 
concretions, with attendant obliteration of details. The supply 
from other localities has been meager, and is preserved in 
widely scattered institutions. Even where the Ohio material 
has been concentrated in some of our leading museums, facili- 
ties for investigating it have often been lacking. Under such 
conditions progress has necessarily been slow. 
Reference was made in the August number of this journal 
(P. 556) to the discovery of several well-preserved crania of 
Dinichthys pustulosus from the Hamilton Limestone, which 
