162 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



Def^n-iptioii. — " Shell ^^^lbglobose, somewhat compressed, adult with eight sinuous 

 constrictions feebly marked on the oiiter surface of the test, but very distinct on 

 internal casts ; greatest thickness at the margin of the umbilicus, five-eighths of the 

 diameter of the shell ; height of outer whorl rather more than three-sevenths of 

 the diameter of the shell. ^Miorls six to eight ; inclusion almost complete ; 

 umbilicus rather small, exposing the edges of the inner whorls, about one-sixth of 

 the diameter in width. Whorl semilunate in section, wider than high ; indented to 

 nearly two-thirds of its height by the preceding whorl ; periphery broadl}- convex ; 

 sides feel>ly convex, somewhat flattened ; inner area nearly perpendicular to the 

 plane of symmetry, slightly concave. Body-chamber occupying a complete whorl ; 

 aperture not seen. Chambers not very deep, about twenty in a whorl in an adult 

 shell. [Suture-hne as in PI. XLII, fig. 3, and PI. XLIII, figs. 2 a, h.] Test thin, 

 with fine spiral strife which in the adult shell are crossed by transverse sinuous 

 incised lines forming a wide forwardly directed concave sinus on the periphery ; 

 it is thickened at intervals so as to produce well-marked constrictions on internal 

 casts. ( ' TVrinkle-layer ' composed of minute, coarse, wavy, anastomosing ruga?.) 

 Shell attaining a diameter of 85 mm." (' Cat. Foss. Ceph. British Museum,' loc. cit.) 



Affiuifies. — This species, though closely related to G. spha^rinim, Martin, is 

 distinguished therefrom by its more compressed form and liy the spiral lines with 

 which its test is ornamented ; the suture-lines of the two species also differ some- 

 what from each other. 



licmarlis. — Owing probably to the absence of the test, or to other defects, this 

 species has sometimes been mistaken for Gh/j)hioceras spha^ricnm, Martin, as may 

 be seen by looking at the list of references above. It seems to be rare in Ireland ; 

 Phillips has no record for it there, and M'Coy (' Synopsis ') has only one, nor docs 

 he figure the species. The specimens at my disposal are all more or less crushed 

 fragments, but the sutiires and ornamentation are well preserved, and this has 

 made the i-ecoguition of the species possible. There being no illustrations of the 

 species in any work treating of Irish fossils, I have figured in PI. XLIII a fine 

 specimen from Derbyshire contained in the British Museum, in addition to those 

 imperfect ones from the black shale figured in PI. XLII. 



Localitir.'^. — Coiirtlough, Garristown, and Newton, county of Dublin; Drumscra, 

 near Druraquin, county of Tyrone (Sir R. GriflSth's ' Localities of the Irish 

 Carboniferous Fossils,' added in 1862 to M'Coy's ' SjTiopsis'). 



