394 On the Fossil Fishes of the Carboniferous Limestone Series of Great Britawn. 
Orodus compressus, M‘Coy. 
(IB, Ib, i847, Iil,)) 
Orodus compressus—M ‘Coy, 1848. “Ann. and Mag. Nat. Hist.,” 2nd Ser., Vol. IL, p- 131. 
» * F. J. Pictet, 1854. “Traité de Paléont.,” Vol. IL, p. 264. 
5 J. Morris, 1854. “Cat. Brit. Foss.,” p. 335. 
a 5 Morris & Roberts, 1862. “Quart. Journ. Geol. Soc.,” Vol. XVIITI., p. 101. 
95 J. J. Bigsby, 1878. ‘‘Thesaurus Devonico-Carb.,” p. 359, 
Teeth, ‘much compressed, crown elevated into a thin edge of equal height 
throughout, surmounted by a fine ridge, and festooned by four or five sharp points on 
each side ; the centre has a large point, producing a globular swelling in the middle 
of each of the flattened sides, over which it sends a small flexuous ridge, giving out 
short branches on each side, while the lateral points only send short simple ridges 
not half way down the sides; ends abruptly truncated; base surrounded by a 
sharply defined thickened border ; surface smooth; highly polished ; root nearly 
as deep as the crown is high; truncated below and at the ends; height of crown 
one line, width of base three and a half lines.” —(M‘Coy,.) 
This species is one of the smallest found in Britain. . The thin compressed edge 
of the crown is a character possessed by Orodus carinatus, St. J. and W. 
(‘“Paleont. Illinois,” Vol. VI., p. 307, pl. v., fig. 24.) but the detailed surface markings 
are quite distinct from that species. 
Formation and locality : Mountain Limestone, Armagh. 
Ez coll: Museum, Geological Society, Burlington House. 
Orodus elongatus, Agass. (MSS.) 
(Weal Ibi he, sarees, il, 2, Bs) 
Teeth, medium size, extremely long in proportion to the width; transverse 
diameter 1:75 inches, antero-posterior diameter *25 of an inch in the centre, barely 
more than ‘1 of an inch on each side, lateral terminations rounded. Central promi- 
nence moderately elevated, with a ridge extending across from the anterior to the 
posterior margins, lateral prolongations unequal, one more depressed than the other, 
branching at right angles from the ridge across the central cone, two lateral ridges 
descend to the right and left extremities respectively, from the lateral carina nume- 
rous secondary ridges branch out on either side, of these the smaller disappear, 
or two frequently converge, forming a Y-shaped fold, the lower portion of which 
becomes attenuated or disappears before reaching the basal margin ; the latter 
smooth and slightly sulcated. Root large, transversely a little wider than the crown, 
central part and shorter extremity twice the depth of the crown, towards the 
longer and more depressed extremity the root is proportionately smaller, base of 
root smooth and straight, except a slight median concavity. Structure porous 
and open. 
This species differs from Orodus angustus, Ag., in the possession of a median 
carina and in the prominence of the central cone. It is also longer and more 
