192 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



1897. Gtlyphioceras spirale, A. H. Foord and G. C. Crick. Cat. Foss. Ceph. 



British Museum, pt. 3, p. 210, 

 fig. 101 (suture-line). 



1901. Wheelton Hind and J. A. Howe. Quart. Jouru. 



G-eol. Soc, vol. lvii, p. 356, etc. 



1902. Wheelton Hind. Brit. Assoc. Adv. Sci., Glasgow, 



1901, p. 289, etc., "Life-zones 

 in the British Carboniferous 

 Rocks." 



1903. Ibid., Belfast, 1902, p. 217, "Life- 



zones in the British Carbo- 

 niferous Rocks." 



Description. — Shell discoidal ; whorls broad and apparently almost completely 

 overlapping each other, thus leaving a very small umbilicus. Test ornamented with 

 numerous fine, regular, spiral lines, which, so far as can be ascertained, are of a 

 delicate thread-like character, varying according to the size of the specimen 

 from '5 mm. to 1 mm. apart. These are crossed by a multitude of extremely deli- 

 cate lines which in cutting the former produce in them a granular appearance, but 

 so fine as to be scarcely visible to the naked eye. 



Dimensions. 



Large specimen from Summer Hill, Specimen figured, 



County of Meath, in Dublin PI. XLIX, 



Mus. Sci. and Art. fig. 9. 



Diameter of shell . . 61 mm. . 33*0 mm. 



,, umbilicus . . — . 3*5 ,, 



Height of outer whorl . . 31 ,, . 15'0 ,, 



These dimensions must be taken as only approximately correct, as the specimens 

 are crushed perfectly flat. 



The true form of this species has not been preserved in the fissile shales in which 

 it occurs in this country, nor yet in England, as we learn from Phillips, 1 and recently 

 from Wheelton Hind; but F. A. Roemer 2 figures an uncrushed specimen which 

 indicates a shell of a somewhat compressed form, having the following measurements 

 (derived from the figure) : — diameter of shell 24 mm., height of outer whorl 12 mm., 

 diameter of umbilicus 5 mm. Thickness of shell at umbilical margin 10 mm. 



Roemer states that the number of spiral lines upon the last whorl is about fifty, 

 and that the spaces between them are covered with much finer transverse lines. 



Affinities. — Fragments of Glyphioceras (Beyrichoceras) striatum with the test well 

 preserved have been mistaken for the present species ; it would seem, therefore, that 

 in respect to ornamentation there is some resemblance between the two species ; 



1 Pal. Foss. Cornwall, Devon, and West Somerset, 1841, p. 121 . 



2 Palaeontograpluca, 1862-4, vol. ix, pi. iv, figs. 2 a — c. 



