CARBONIFEROUS FOSSILS OF IRELAND. 11 



AcTiNOCEKAS. Sfokes. 



Gen. Ch. — Siphunclc containing an internal tube connected with the walls of the siphuncle by radiating 

 lamellae. 



ACTINOCERAS GIGANTEUM. SoW. SP. 



Orthocera gigantea. — Sow. Min. Con — .Actinocoras Simmsii. — Stokes, Gaol. Trans. 



Sp. Ch. — Elongate conic, smooth, or faintly striated across ; siphuncle excentric, monlllform, internally 

 compound as in Ormoceras, radii about four (?), septa numerous, concave, composed of several thick lamella. 



I have ascertained that this fossil has precisely the same structure of siphuncle, both in external form and 

 internal complexity, as we see in the Ormoceras Batjfieldii : in fact, from the sections I have made, I do not 

 find a single character to distinguish the genera Actiiioceras and Ormoceras from each other. The Ortliocerax 

 giganteum of Sowerby presents all the characters, both of size and external and internal conformation, of the 

 Actinoceras Simmsii of Stokes. I have, therefore, restored the old specific name, but retained Mr. Stokes' 

 generic name. Common in the red limestone of Castle Espie Comber, where it sometimes attains a length of 

 tour teet, imperfect at each end. Sowerby, in the Min. Con., when describing the O. giganteum, notices its oc- 

 currence in this locality. 



ACTINOCEKAS PYRAMIDATUM. M'Coy. (PI. I. fig. 5). 



Sp. Ch. — Rapidly tapering; siphuncle moniliform, contracted between the septa, longitudinally wrin- 

 kled, internal tube small, radiating lamella, three or four ; septa double, having a considerable space between 

 the layers on one side. 



This species is easily distinguished from the A. giganteum ( <Sw?w«S22 of Stokes) by the rapidity with 

 which it tapers and the simplicity of the siphuncle. 



Cyrtoceras. Oold. 



Gen. Ch. — Involute, slightly depressed ; whorls disjoined; septa simple, sijihuncle dorsal. 



Cyrtoceras tuberculatum. M'Coy. (PL IV. fig. 2). 



Sp. Ch. — Elongate, tapering, slightly curved ; section very broad, oval ; surface with about twenty-six 

 nan-ow, equal, longitudinal ridges, strongly and regularly tuberculated ; intervening spases rather broader than 

 the ridges, shallow, concave, smooth. 



In proportions, curvature, and number of ridges, this closely resembles the O. Gesneri, Mart., but difltrs in 

 the tuberculation of the ridges. The smooth intervening spaces, and nodular (not scale-like) tuberculation of the 

 ridges, separates it from the C. quindeclmale and C. ohliquatum; the form of the latter is also perfectly distinct. 

 A specimen, imperfect at both ends, one inch and seven lines in length, and eight lines in width at the base, 

 tapers to five lines. 



Phragmoceras. Brod. 



Gen. Ch. — Involute compressed, conical; septa simple, crossed by the lines of growth ; siphuncle usually 

 ventral ; mouth contracted, outer extremity produced. 



Phragmoceras flexistria. (PL I. fig. 1). M'Coy. 



Sp. Ch. — Discoid, compressed, involute, surface marked with numerous coarse, waving, longitudinal stria3, 

 crossed by fine sigmoidal wrinkles of growth. 



