102 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



Dimensions. 



Diameter of shell 



,, umbilicus (from edge to edge) 

 ,, ., (from suture to suture) 



Height of outer whorl (dorso- ventral) 

 Width of periphery of outer whorl 



Specimen from Glenbaiie, 

 Limerick. 



64 mm. 

 40 „ 

 30 „ 



16 „ 

 20 ,. 



Affinities. — This species may be compared with T. Hyatti, but the resemblance 

 between them is of a very general character, the differences that distinguish them 

 being, on the other hand, very strongly marked. Looking first at the points of 

 agreement, we find that, like T. Eyatti, T. Eihernicum is ornamented with longi- 

 tudinal ridges which cover the whole of the shell, and that the general form of 

 the latter is distinctly subquadrangular, with a flattened peripheral area and a 

 somewhat obscurely defined separation between the sides and the umbilical 

 declivities. The differences consist, firstly, in the presence of distinct crenulations 

 formed at the intersection of the two systems of lines which ornament the shell in 

 T. Hibernicum which are not present in T. Hyatti ; secondly, the ornamentation is 

 coarser in the former than in the latter, and it would seem, though my material 

 does not admit of certainty on this point, that the central vacuity is larger in 

 T. Hibernicum than in T. Hyatti. 



Remarks. — Hyatt referred this species rather doubtfully to his genus Rineceras, 

 but though the ornamentation may suggest afiinities with the members of that 

 genus, of which R. p-opinquum, de Koninck, is taken as the type, yet the form of 

 the whorls and the close coiling indicate connection with another series of forms, 

 and, after much deliberation, I have decided to include it in that of Thrincoceras. 



Locality. — G-lenbane, county of Limerick ; near Dublin,^ 



Genus Discitocekas, Hyatt, 1883 (emend. 1893). 

 DisciTOCERAs Levf.illeanum, L. G. de KonincJ,-, sp. Plate XXVII, figs. 1 — 3. 



1844. Nautilus Leveilleanus, L. G. de Koninck. Descrip. Aniru. Foss. Terr. 



Carb. Belgique, p. 552, pi. xlix, fig. 1 (pi. x.xv, 

 fig. 1 excl.). 

 1878. — — L. G. de Koninck. Fauiie Calc. Carb. Belgique 



(Ann. Mu8. Roy. d'Hist. jN'at. Belgique, 

 Paleont., torn, ii), pt. 1. p. 143, pi. zxviii, 

 fig. 6. 

 1S91. DisciTKs Leveilleanus, ji. H. Foard. Cat. Fobs. Cepii. British Museum, 



pt. 2. p. 88. 



' Briti^ii Museum specimeD, " Catalogue," loc. cit. 



