172 CAEBONIFEROFS CEPHALOPODA OF IRELAND. 



iniglit have been established. On the other hand, the numerous constrictions some- 

 times present in G. Ei><ji<iuii-inn appear to be entirely wanting in (i. tlifficih-, 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 availal)le. 



GhjpMoceras {Bcyrichocern.^) difficile may, however, very appropriately take its 

 place in the group of G. {B.) trancatum 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, coimty of Limerick. 



Gi,TrHiocERAS (Betrichoceeas) SFBQUADEATUif, sp. uov. Plate XL VI, figs. 2 a — r. 



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

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

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

 whorls exposed only at their edges; inclusion nearly comj^lete. ^^Hiorl subrpiadrate 

 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 sigmoidal 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. 



From these dimensions it will be seen that the specimen measured lias lieen 

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



