FISHES OF THE CARBONIFEROUS SYSTEM. 145 
the relative positions they occupied in the fin. One such group of fin rays 
is shown in Pl. VII, Fig. 1. 
The individual rays are from two and a half to three and a half inches 
in length, quadrangular in section, half an inch broad by three-eighths 
thick. They are composed of a shell of dense bony tissue surrounding a 
zavity which, in uncrushed specimens, is now filled with pyrites, and was 
probably once occupied by cartilage. The articulations are not preserved, 
and they were apparently cartilaginous. These fin rays probably represent 
the first or basal row; the exterior subdivisions having disappeared, perhaps 
because they were cartilaginous, perhaps because they had been eaten away 
by some of the smaller fishes of the sea in which Dinichthys lived. 
From the numbers of fin rays found together, a dozen or more, and 
these forming only part of the base of the fin, as well as from their strength, 
straightness, and symmetry, I am inclined to consider such groups as that 
now figured as belonging to the dorsal fin. 
Remains of the pectoral fins of Dinichthys have been earnestly sought 
for, and it seems probable that they have finally been found. In the remains 
of Coccosteus studied by Hugh Miller, Agassiz, and Sir Philip Egerton no 
traces of pectoral fins were met with, though a dorsal fin is frequently trace- 
able in their specimens. Recently Prof. A. von Koenen, of Gottingen, has 
discovered, in connection with some unusually well-preserved specimens of 
Coccosteus, what he considers as the ‘‘ruder organe,” or pectoral fin spine. 
This is straight and staff-like, rounded at its anterior, pointed at its pos- 
terior extremity; on its outer face it is ornamented with the characteristic 
tubercles of Coccosteus, within rough or longitudinally striated, as though 
for the attachment of muscles, a fin membrane, or soft fin rays. 
The zoologic affinity between Dinichthys and Coccosteus is so intimate, 
that it was to be expected if Coccosteus had fin spines, something of the kind 
would be found with the remains of Dinichthys, and I am now able to report 
the probable discovery of these. Alongside the outer margin of the plates 
composing the ventral shield, detached, splint-like bones have several times 
been noticed, of which the position and use have till now been unsuspected. 
' Beitrag zur Kenntniss der Placodermen, Abhandl. kénig. Gesell. d, Wissen. zu Gottingen, vol. 
30, 1883. 
MON xvI——10 
