ON SOME ARMOURED FISHES. 
15 
We come next to the genus Coccosteus* of Agassiz, in which, 
as in Pterichthys , already noticed, the dermal armature was 
composed of numerous plates, soldered together at their sutures, 
like 44 trusty knight in armour dight ” — furnished with both 
back and breast-plate well rivetted together. 
The external surface of these bony buckler plates in Coccos - 
teus is ornamented with small hemispherical tubercles ; from 
this fact the generic name, signifying 44 berry-bone,” is derived. 
The similarity of this ornamentation to that of the plates of the 
buckler in some tortoises led to the belief, when these coccosteal 
plates were first discovered, that they were evidence of the pre- 
sence of Chelonians in the Devonian beds. They have even been 
regarded at one time as parts of some crustacean carapace. 
Alluding to Pander’s restoration (PI. II., Fig. 1), Professor 
Owen remarks :f 44 If a heterocercal fin were added to the restora- 
tion, a correct idea would be given of the Old Red fossii, which, 
in the progress of its construction, has suggested such diverse 
notions of its nature and affinities. 
44 The helmet and cuirass are firmly united, and there is no 
trace of the jointed appendages, like pectoral fins, which 
characterize Pterichthys (PI. I., Fig. 5, c, c). The unprotected 
part of the trunk shows an ossification of the neural and haemal 
spines (n and h ), and of their appendages, the rays of the 
4 dorsal’ and 4 anal ’ fin ( d and a); and by the analogy of 
Cephalaspis (PI. I., Fig. 4), the tail was most probably terminated 
by an unequal-lobed fin (c). The lower jaw is composed of two 
rami, loosely connected at the symphysis ; so that being displaced 
and crushed in fossil specimens, they gave rise to the notion of 
the fish being provided with laterally-moving jaws, like those of 
the lobster. But the lower jaw worked vertically upon a fixed 
upper one ; both jaws being provided with from ten to twelve 
teeth on each side, anchylosed to the bone.” 
The blank space (ch) seen in fossil specimens, between the 
neural ( n ) and haemal ( h ) spines, indicates the position of the 
soft 44 notochord ” which has been dissolved away. The cylin- 
drical gelatinous body, so-called (in Latin chorda dorsalis ), 
exists before the formation of the bony bodies, or centra , of the 
vertebrae in all vertebrate animals : and the development of 
those bodies seems never to have gone beyond this embryonal 
phase in any palaeozoic fish. Hence the} 7 have been called 
44 notochordal ” fish, on account of their retaining the noto- 
chord. (Owen.) 
* So called from kqkkos a berry, and oareSu bone, in allusion to the 
surface of the plates being everywhere cohered with smoll berry-like 
tubercle 3 . (See Woodcut, Pig. 10r?, JEukeraspis, but which conveys a good 
idea of the surface ornamentation of Coccosteus.) 
t u Palaeontology,” p. 145. 
