616 BRITISH PALZEOZOIC FOSSILS. [ Pisces. 
marked with from three to six punctured, impressed, longitudinal strize, and in most parts of each of the spaces 
is found a scattered, irregular row of the smooth, pointed, rather distant tubercles of the genus. 
Position and Locality—Not very uncommon in the lower carboniferous limestone of Armagh. 
Explanation of Figures—PI. 3. K. fig. 28, portion of spine near base imperfect at each end, natural 
size, from the carboniferous limestone of Armagh; fig. 23 @, ditto section near base; fig. 24, ditto nearer to the 
apex ; fig. 24a, ditto portion of surface magnified. 
ASTEROPTYCHIUS SEMIORNATUS (J/°Coy). PI. 3. K. fig. 22. 
Dese.—Ray slightly arched, about three lines wide, and tapering at the rate of about one line in one inch ; 
section much compressed, the sides being flattened, and the thickness about one-third the width; about seven 
or eight narrow longitudinal smooth ridges on each side, separated by flat spaces nearly twice the width of the 
ridges ; all the spaces are marked with two or three obsolete longitudinal striz, but only the anterior one on 
each side contains a row of irregularly placed tubercles. 
This species strongly differs from the A. ornatus by having at the same size double the number of longi- 
tudinal ridges on each side, they are also closer and more regular. This is also rather more compressed and 
arched than the A. ornatus (Ag.), and differs besides in haying but one row of tubercles on each side, while 
that species has a row in nearly every space. 
Position and Locality —Rare in the Armagh limestone. 
Explanation of Figures —P1. 3. K. fig. 22, portion of spine imperfect at each end; fig. 22 a, ditto por- 
tions of surface magnified, shewing the single row of tubercles, 
Genus. CHIRODUS (MCoy). 
(Etym. yelp, manus, and é8ovs, dens.) 
Gen. Char.—General form of Ceratodus, that is, more or less fan-shaped, thick, flattened, with the anterior 
broad margin deeply divided into lobes; but the inner nearly straight margin has a small, recurved, thumb-like 
lobe projecting nearly at right angles from the middle of its length (preventing the mesial junction of the 
_tritors of each side of the jaw); the inner marginal lobe is the longest ; surface minutely punctured. 
The only specimen which has occurred to me of this genus presents merely two lobes in the anterior margin, 
but as the outer edge is imperfect there may have been another lobe, but I think not more. I should have 
referred the tooth to the Permian genus Ceratodus, but that the inner margin (which in Ceratodus is straight 
to fit the similar edge of the tooth on the other side of the jaw) has got a small lobe projecting horizontally 
inwards from its middle, which would prevent such a union; or if it be viewed as possibly the outer margin, 
we should have the equally singular characters not only of so great a disparity in size between two adjacent 
lobes, but the principal marginal lobes would increase in size from within outwards, which would be contrary 
to all analogy. Hence, independent of the geological importance of not extending unnecessarily the vertical 
range of a genus, we find it zoologically impossible to group together teeth so differently constructed that 
they could not be similarly arranged in the mouth. I have named the genus from the general resemblance 
to a hand, or still more to the foot of a Ohirotherium, in miniature. 
CHIRODUS PES-RANZ (M/°Coy). Pl. 3. G. fig. 9. 
Ref.—Id. M°Coy, Ann. and Mag. Nat. Hist. 2nd Series, Vol. IT. 
Desc.—Length eight lines, narrow; anterior lobes narrow, prominent, rounded, arched, separated by deep 
concave furrows; the inner lobe about a line longer than the next outer one; at the base of the former, or 
about half the length of the whole tooth, there projects horizontally inwards from the inner margin a short, 
wide, slightly recurved, flattened lobe, about one line long; posterior part of the tooth flattened ; surface finely 
punctured under the lens. 
