GLYPHIOCERAS (BEYRICHOCERAS) SUBRETICULATUM. 185 



height of outer whorl in the same proportion. Number of whorls unknown ; 

 inclusion nearly complete. Umbilicus probably rather deep, almost exactly one- 

 fourth of the diameter of the shell in width, with a subangular margin and steep 

 inner area. Whorl semi-oval in section, height and width nearly equal; indented 

 to about one-third of its height by the preceding whorl. Periphery narrowly 

 convex, separated from the sides by an obscure ridge. Sides flattened. Extent 

 of body-chamber unknown. Chambers shallow. Suture-line as in PI. XLIX, 

 fig. 7 d. Test covered by a multitude of delicate, regular, crenulated lines, which 

 bifurcate near the umbilical margin. At intervals one or two of the lines are 

 elevated slightly above the others, giving the appearance of slight ridges where 

 this occurs. The lines are distinctly sigmoid in crossing the sides of the shell. 

 Starting from the umbilical margin they curve slightly backwards at about the 

 middle of the sides, then curve strongly forwards and again backwards upon the 

 periphery, where they make a deep linguiform sinus. Faint spiral lines, a little 

 stronger near the periphery, cover the whole of the test. Tavo broad and shallow 

 constrictions crossing the sides and periphery in the same direction as the 

 crenulated lines appear upon the cast. No trace of constrictions can be seen 

 where the shell is present. 



Dimensions. 



Specimen in the Dublin Mus. 



Sci. and Art (Geol. Surv. 



Coll.), No. 845 C. 



Diameter of shell .... 23"0 mm. 



,, umbilicus . . 5" 5 ,, 



Height of outer whorl . . . 12*0 ,, 



,, above preceding whorl . . 8 - ,, 



Thickness at umbilical margin . . . 11*0 „ 



Affinities. — From the nature of the ornaments this species would appear to 

 belong to the reticulatum group, but it is a much more compressed shell and the 

 reticulations much finer than in GlypMoceras (Beyrichoceras) reticulatum itself; the 

 umbilicus is also much smaller in the present species than in the Latter. The 

 suture-line is characterised by the obtuse form of the lateral lobe, at least in the 

 young shell, the suture of which is figured (PL XLIX, fig. 7 d). When the septa 

 are not seen the ornamentation of the shell will suffice for the recognition of the 

 species. Another specimen from the same locality, and I believe the same band of 

 rock, is doubtfully referred to this species. It is a east of the greater part of the 

 body-chamber, with the septa, which arc somewhat eroded, occupying about one- 

 third of the whorl. The ornamentation is obscurely seen upon the cast ; it 

 resembles that of the present species. A very line keel extends along the median 

 line of the periphery (PI. XLIX, fig. 6 &). 



Locality. — Foynes Island, county of Limerick. 



