CARBONIFEROUS FOSSILS OF IRELAND. 9 



This species differs from the O. laterale, Pliil. 0. imhricatum, Wal. and O. tmdulatum, Sow., in its 

 very distant chambers, and from the last species by its nearly central siphuncle ; it also tapers more rapidly 

 than any of those species. Length of specimen, imperfect at both ends, two inches, three lines, long diameter 

 at base, one inch one line, sliort diameter nine lines. 



Orthoceras (Loxoceras) incomitatum. M'Col/. (PL I. fig. 6). 



Sp. Ch. — Conical, very rapidly tapering towards the apex; section broad oval; septa slightly oblique, 

 without wave, or vni\\ a very slight one, slightly convex, varying from a fifth to a sixth of their longest diame- 

 ter in distance from each other; sljjhuncle slightly excentric. 



In the great approximation of the septa, this species resembles the O. /mirica^Mjn, Wahl., but differs in its 

 short, conical form towards the apex, and the sej)ta wanting the strong lateral wave of that species ; it is perhaps 

 most nearly allied to the O. cyUndraceiim, Flem., but differs in its proportion, section, and siphuncle. One 

 specimen of the last, chamber ten lines long, and seven lines in diameter at the base, tapers two lines ; a spe- 

 cimen, near the apex one inch two lines long, and five lines in diameter at the base, tapered four lines ; the 

 septa vary from one-half, to one and a half lines apart. Very common in the black slate of Cove of Cork, 

 but has not occurred elsewhere, and it is unaccompanied by any other fossil. 



Orthoceras (Loxoceras) laterale. Phil. sp. 



Orthocera undulatum. Sow. Min. Con Orthoceras undulatum and Orthoceras laterale. Phil. Geol. York. — Ortlioceras 



laterale. Phil. Pal. Foss. Orthoceras subimbricatum. Portk. Geol. Kep. 



Sp. Ch. — Shell tapering, thin, smooth; septa numerous, oblique, their edges rising with a wave on each 

 side ; about one and a half lines distant from each other ; siphuncle excentric ; section oval. 



This species is very remarkable for the two lobes in the edge of the septa ; a specimen two inches long 

 and one inch in diameter at the base, tapers four lines. 



Orthoceras (Trigonoceras) paradoxicum. Sow. sp. 



Ortliocera paradoxica. Sow. Min. Con. 



Sp. Ch. — Shell rapidly tapering, abruptly curved towards the apex; back flat, bounded by two prominent 

 rounded keels ; front angular, rounded ; sides convex in the middle, equal in width to the back ; surface smooth ; 

 siphuncle nearly central. 



The only perfect specimen I have seen, of this curious shell, is in the Collection of the Rev. Dr. Sirr, 

 from the lower limestone of Kildare. 



Orthoceras (Campyloceras) arcuatum. Phil. sp. 



Orthoceras arcuatum. Phil. Geol. York. 



Sp. Ch. — Obliquely conical, short, very rapidly enlarging, arched towards the apex; septa very nume- 

 rous ; siphuncle dorsal. 



This is the shortest species of the genus with which I am acquainted, and is easily distinguished by its 

 curved form and smooth surface. 



Orthoceras (Campyloceras) unguis. Phil. sp. 



Orthoceras unguis. Phil. Geol. York. 

 Sp. Ch. — Elongate, tapering, smooth, curved towards the apex; septa simple, approximate, from one and 

 a half to two lines apart; siphuncle nearly dorsal. 



This species is larger, and tapers much more gradually than the O. arcuatum, to which it is otherwise 



similar. 



C 



