lsl CARBONIFEROUS CEPHALOPODA OF IRELAND. 



than one-half of the diameter of the shell. Whorls six or seven ; inclusion almost 

 complete ; umbilicus about one-fourth of the diameter of the shell in width, with 

 angular margin and sloping sides. Whorl obtusely sagittate in section, rather 

 higher than wide ; indented to a little more than one-half of its height by the 

 preceding whorl ; periphery subangular ; sides feebly convex, with an obtuse spiral 

 ridge near their centre ; inner area rather narrow, well defined, flattened, sloping 

 towards the umbilicus. Body-chamber occupying a complete whorl. Chambers 

 rather shallow. . . . Test thin, delicately reticulate; the transverse strias very 

 finely crenulate, strongly arched forward near the periphery, and forming thereon 

 a deep broad sinus ; its inner surface with angulated thickenings, producing con- 

 strictions on the internal cast. Initial chamber small, transversely ovoid." 



" Immature forms differ from the adult in being less inflated and in having 

 a more convex periphery. The constrictions are scarcely visible on the test, but 

 are well marked on the internal cast. By breaking back and by sectioning adult 

 examples we have been able to satisfy ourselves that the young stages are what 

 have been named Gon, Gibsoni; these not uncommonly have a slightly sulcated 

 periphery (more conspicuous in an internal cast), and have been described as 



Go II. JU(J0SUS." 



" Shell attaining a diameter of about -15 mm." (' Cat. Foss. Ceph. Brit. Mus.,' 

 loc. cit.) 



Affinities. — The relationship of the present species to Glyjphioceras (Beyrichoceras) 

 excavatum is referred to under the description of that species ; it has also some 

 affinities with G. (B.) Davisi, Foord and Crick, 1 but the latter has a more inflated 

 form and an acutely angular periphery. 



Remarks. — This species is represented in the " Griffith Collection " only by 

 some crushed fragments in shale, but the characteristic ornamentation sufficed for 

 its determination. The specimens are, however, not in a condition to serve for 

 illustration. 



Localities. — Mullagh tinny (Cloger), county of Tyrone; Doon, Mount Phelim, 

 one mile south-west of Kilfendra, county of Clare ; Paget Priory, five miles north 

 of Maynooth — a local name,— county of Meath (the specimen from the last-named 

 locality is labelled " Goniatites Gibsoni") ; Rathcahill, near Abbey field, county of 

 Limerick. 



GrLYPHIOCEBAS (BeYEICHOCEBAs) SUBRETICULATUM, sp. UOV. Plate XLIX, figs. 6 a, b, 



7 a — (I. 



Description. — Shell (young ?) discoidal, compressed, umbilicated; greatest thick- 

 ness a1 the edge of the umbilicus, about one-half of the diameter of the shell ; 



1 ' Cat. Foss. Ceph. British Museum,' part iii, 1897, p. 11)8, figs. 95 a—c. 



