Pisces. | UPPER PALZOZOIC VERTEBRATA. 627 
sloping outwards, and terminating in an obtuse angle in the middle, and directed downwards, and outwards; 
the very prominent base of the crown being surrounded by three or four flat imbricating bands of ganoine ; 
root abruptly flattened, also narrower than the crown, and about equalling it in depth. Average width of 
limestone specimens six lines, depth of crown two lines, depth of root the same, width of root four and half 
lines; rarely one inch wide, when the depth of root and crown together is seven lines. 
The coronal bands of ganoine are broader and apparently more numerous on the inner side, and there 
descend so low with a gentle curvature, that the root is only half the depth of the crown. This species is 
figured under the name C. pectinatus Ag. by Mr Binney, in the Trans. of the Manchester Geol. Soc. Vol. I. 
t. 5. f. 20, 21; but it seems distinct from the C. pectinatus as given in Agassiz, Poiss. Foss., like which 
figures I have never seen anything in nature; but if they be accurate, I think (as I believe M. Agassiz does 
also) that the present species must be distinct. 
Position and Locality.—N ot uncommon in the lower carboniferous limestone of Armagh ; rare, of large size, 
in the black carboniferous limestone shales of Derbyshire. 
Explanation of Figures.—PI. 3. I. fig. 21, view of average-sized tooth, on inner aspect (the transverse 
folds at base of crown broken off); fig. 21 a, portion of crown and cutting edge magnified, shewing a serration 
of the denticulations; fig. 22, smaller specimen, natural size, front view; fig. 22a, portion of ditto magnified, 
shewing the variety with smooth lobes to the cutting edge; fig. 23, large specimen, inner view, root perfect in 
depth, but imperfect at the sides. 
Genus. DIPRIACANTHUS (Af Coy). 
(Etym. ds, bis, mplov, serra, and dxavba, aculeus.) 
Gen, Char—Spine small, arched, tapering, much compressed, minutely and irregularly tuberculated; two 
rows of small conical teeth on the posterior margin, and two rows of larger adpressed teeth on the anterior face 
directed upwards. 
The spines for which I propose this name, are easily recognised by their small size, curved form, and having 
the anterior as well as the posterior margin armed with rows of teeth. These characters, while they separate 
them widely from the other fossil spines, strongly recal to our mind the Pimelodes and Synodonts of the Nile ; 
in fact, the Synodontes serratus described by Riippell* is a perfect prototype in its spinous defences of our 
Dipriacanthus falcatus, except that both the anterior and posterior rows of teeth are single on the recent 
spines. In their compressed section and irregularly tuberculated surface the Dipriacanths resemble the 
Oracanths, but are distinguished by their arched figure and rows of teeth. 
Diprracantuus Stoxesit (A7*Coy). Pl. 3. K. fig. 18. 
Dese.—Slightly arched, much compressed, sides flat, anterior and posterior margins narrow, obtusely 
rounded ; section oblong, the long diameter being from four to five times longer than the short; teeth of the 
posterior margin slender, conical, projecting at right angles to the spine; teeth of the anterior margin large, 
thick, smooth, the upper sharp edge widest, closely adpressed to the surface ; surface closely covered with small, 
irregular, smooth granules, which under a strong lens are found to be radiatingly striated at their base, and with 
the intervening narrow spaces very minutely granulated. 
When highly magnified the granulation of this spine resembles on a small scale the star-like style of orna- 
ment of the bony plates of Asterolepis (Eich.). The base is imperfect, but apparently dilated in a remarkable 
degree, and in its present state the lower portion seems bent at a considerable angle from the curve of the rest 
of the spine. 
Collected from the carboniferous limestone of Armagh by the Rev. W. Stokes, of Caius College, Cambridge, 
and by him presented to the University Collection. I have associated his name with this interesting form as a 
slight memorial of the zeal with which he has collected these remains, and the liberality with which he has made 
them available for public instruction. 
Lxplanation of Figures.—P1. 3. K. fig. 18, natural size; fig. 18 a, ditto, portion magnified. 
* Beschreibung und Abbildung never mehrere Fische, im Nil entdeckt. Frankfort a. M. 1829, plate 2. fig. 1. 
