594 BRITISH PALAZOZOIC FOSSILS. [ Pisces. 
Hotorrycuius ANDERSONI (Ag.) 
Ref. and Syn —Ag. Old Red, t. 22. f. 3+ H. Flemingi id. ib. f. 1. 
Desc.—F usiform, abruptly contracted at the pedicle of the tail; head rather small, its length from snout 
to edge of operculum slightly less than its height ; depth of body at origin of dorsal fin about one-fifth more than 
the length of the head; dorsal fin small, originating about one-fifth more than the length of the head behind 
the edge of operculum ; lateral line running beneath the upper third of the sides, commencing at about one- 
fourth the depth from the dorsal outline at the nape, but descending to two-fifths the depth from the dorsal 
outline at the origin of dorsal fin; ventral fins moderate, situated twice the length of the head from the oper- 
culum; scales of moderate size, nearly circular; in a specimen two inches nine lines in depth the exposed 
portions on the middle of the sides average five to six lines in depth and four lines in length, they are marked 
each with about twenty very variable, fine, thread-like ridges, sometimes nearly parallel, less than their thickness 
apart, and scarcely branching or anastomosing ; at other times separated by broader concave spaces and more 
or less flexuous, and anastomosing once or twice as they approach the posterior edges, to which in all the 
varieties they extend (averaging eight in the space of two lines), sometimes they seem smooth and often are 
finely granular, in all cases the anterior part is occupied by a patch of rather coarse radiatingly disposed granules, 
from whence the ridges arise that go to the free edge ; the smooth overlapped portion is marked under the lens 
with very minute, close, punctured, radiating lines; the scales of the belly are larger than those of the sides, 
and much more coarsely sculptured, with thicker, more widely separated, and more flexuous ridges than those of 
the sides (averaging four or five ridges in two lines), the bones of the head are coarsely granulated (about three 
granules in the space of one line), with an imperfect radiating disposition towards the margin of some of the 
plates. 
The very numerous, although fragmentary, specimens which I have examined, prove what I for some time 
suspected, that the more finely and straightly ridged scales on those specimens of Holoptychius from Duraden 
shewing the lateral lines, and forming the type of H. Flemingi, were really identical with those similar fishes 
intermingled with them, but having much more coarsely sculptured scales figured by M. Agassiz under the 
name H. Andersoni. The latter coarsely sculptured species I find is in fact the ventral aspect of the more 
delicately ridged specimens, which are compressed laterally, and it is certain that the two triangular plates in 
M. Agassiz’ figure are the branchiostegal plates, such as we see in the H. nobilissimus, and not of the cranium. 
as Agassiz supposed. The ridges as he states extend to the posterior edge, but, contrary to what he states, 
though in agreement with parts of his figure, they not unfrequently anastomose twice, even three times in their 
passage from the little anterior patch of granules (which he does not represent, probably because they are 
frequently covered by the preceding scales close to the edge). Some very large specimens shew the exposed part 
of the scales eleven lines in depth, and nearly six in length, the ridges averaging five in two lines. The sculp- 
turing of the scales is very irregular, and one specimen of the ventral aspect, having several of the scales 
sculptured in the usual way of H. Andersoni, has the ridges on two or three scales broken into tubercles 
nearly resembling those of H. Murchisoni. 
Position and Locality —Extremely abundant (sometimes nine perfect specimens in a slab two feet square) 
in the yellow uppermost beds of the Old Red sandstone at Duraden. 
HOLOPTYCHIUS GIGANTEUS (Ag.) 
Ref.—Ag. Old Red, t. 24. figs. 3, 4, 8. 
Dese.—Seales very thick, about one inch and half wide; length of exposed portion two-thirds the width, 
posterior margin truncato-elliptical; surface with close, thick, irregularly, tortuous, longitudinal ridges on the 
middle portion, posterior part largely tuberculated 
The great size is almost the only difference between this and the H. Murchisoni, with which perhaps it 
may be hereafter united. The under surface has the usual radiating minutely ceilular structure. 
Position and Locality—Old Red sandstone, Scat Craig. 
