162 TRANSACTIONS OF THE [may 11, 
(C). SupportincG ELEMENTS OF THE DoRSAL AND OF THE 
PeEtvic Fin. 
The position of the basal support of the dorsal fin may be 
outlined in the fossil, Pl. VII., DF, although they are imperfectly 
preserved. In number they correspond closely to those of 
Coccosteus, but in other regards they appear to have been 
widely different; they are thus smaller and slenderer, and the 
elements of their proximal row, although very imperfectly 
shown, seem to have differed considerably from the neighboring 
distal elements. It is also noteworthy that the outer tips of the 
distal elements appear to have been the more densely calcified, 
so that indeed these tips could remain after the remaining por- 
tion of the element had disintegrated. Several of these sepa- 
rated distal ends may be noted in the fossil. The evidence now pre- 
sented is sufficient to demonstrate that the dorsal fin of 
Dinichthys was relatively in the same region as in Coccosteus, 
but that it was smaller and more delicate, the latter character 
directly opposed to what might have been inferred on a priori 
grounds. ; 
The pelvic girdle and the basal supports of the ventral fin 
are shown in the fossil, at VG and VF, Pl. VII. Their preser- 
vation is, however, so imperfect that nothing definite can be de- 
termined about them; indeed were it not that this portion of 
the fossil corresponds so closely in position and outline to the 
structures of the ventral fin and hip girdle in Coccosteus, one 
could hardly be justified in atttempting an identification. The 
writer is inclined to believe that the apparently separate elements 
at VF.are in reality not the basalia of the ventral fins, but 
artificially separated portions of the distal part of the. pelvic 
girdle. 
Fin structures in Dinichthys (terrelli) have already been des- 
eribed by Prof. Newberry, and figured by him in his Palzozoic 
Fishes (Monograph XVI, U. 8S. Geological Survey, Pl. VII.). 
His specimens, however, had been sent him without their ma- 
trix, and he could not therefore determine their exact position. 
They had been received from Ohio from Mr. J. Terrell, who had 
several times found them associated with the bones and plates of 
D. terrelli. These “ ossified fin rays,” as far as Dr. Newberry 
could judge from a single detached group of them, and from 
several fragmentary elements, were then believed to represent 
in part the base of the dorsal fin. The structures of the present 
specimens are certainly not adverse to this view of Dr. Newberry. 
But a reéxamination of the types by the present writer leads to 
the belief that they may well have been exernal fin structures. 
