172 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



might have been established. On the other hand, the numerous constrictions sonic- 

 times present in 0. Hispanicum appear to be entirely wanting in G. difficile, which 

 has also a thicker shell. On the whole it seemed better to give a distinctive name 

 to the Irish species rather than to merge it in the Spanish one upon the imperfect 

 information available. 



Glyphioceras (Beyrichoceras) difficile may, however, very appropriately take its 

 place in the group of G. (P>.) truncatum and its allies. The difficulty I have 

 experienced in separating the forms included in this group is in itself a measure of 

 their very close affinities. 



Locality. — Lisnakerry, county of Limerick. 



G-lyphioceras (Beyriohooeras) subquadratum, sp. nov. Plate XL VI, figs. 2 a — c. 



Description. — Shell discoidal, compressed, sides moderately convex, the peri- 

 phery distinctly flattened, with well-defined lateral angles ; umbilicus rather large, 

 deep ; umbilical zone narrow, nearly perpendicular, the edges subangular. Inner 

 whorls exposed only at their edges; inclusion nearly complete. Whorl subquadrate 

 in section owing to the marked truncation of the periphery ; greatest thickness at 

 the umbilical margin, a little more than five-sevenths of the height. Suture-line 

 as in PI. XLVI, fig. 2 c. Test, seen in a young individual, ornamented with 

 extremely fine imbricating (?) striae, which form a gentle sigmoid al curve in 

 crossing the sides of the shell, and a deeply indented sinus in crossing the 

 periphery. Several shallow constrictions are present on the cast. 



Dimensions. 







Specimen from Little Island, 



Cork, in the Bristol 



Museum. 



Diameter of shell (longer) 



. 78, mm. 



,, „ (shorter) (about) 



. 50 „ 



,, of umbilicus (longer) 



• 20 „ 



,, ,, (shorter) . 



• 17 „ 



Height of outer whorl . 



• 35 „ 



Thickness at umbilical margin 



• 28 „ 



From these dimensions it will be seen that the specimen measured has been 

 distorted into an elliptical shape, and this is precisely the case with another 

 specimen from the same locality from which the suture-line (PI. XLVI, fig. 2 c) 

 has been drawn. 



Affinities.— Notwithstanding the much greater size of the umbilicus in this 

 species compared with that which is met with in species belonging to the group 



