GLYPHIOCERAS (MTJENSTEROCERAS) CRASSUM. 193 



but it is little 1 more than superficial. Tn G. (/>.) striatum the shell is more inflated 

 than in G. (I I.) sjpirale, and the spiral lines in the latter are wider apart than they 

 are in the former. There is considerable difference also in the form of the suture- 

 line in the two species. But although distinguishable even in fragments there can 

 hardly be any question as to their close relationship. Spiral ornamentation seems 

 to be as rare among the Goniatites as the corresponding longitudinal ornamentation 

 is among the straight-shelled Nautiloidea (Orthoceratites), or spiral ornaments 

 in the coiled ones excepting in the younger stages of growth. 



The "Goniatites" granosus of Portlock appears to represent only a particular 

 state of preservation of Glyphioceras spirale in which the transverse lines are more 

 conspicuous than they are in the casts of the shell usually met with. It is there- 

 fore included among the synonymy of the latter as in the ' Catalogue of Fossil Cepha- 

 lopoda, British Museum,' part iii. 



Remarks. — The slaty character of the deposits in which this species occurs has 

 been fatal to its good preservation, and it appears only in the shape of casts crushed 

 perfectly flat between the thin papery layers of the rock. Fragments of the test 

 with its fine thread-like lines are sometimes seen scattered near the crushed shells, 

 but it is usually met with in the condition of casts consisting of a series of regular, 

 parallel incised lines crossed by curved transverse lines scarcely visible to the naked 

 eye. The figure of this species on PL XLIX (fig. 9) shows very well the condi- 

 tion in which the species usually occurs. 



The largest complete specimen measures 55 mm. in diameter. This is from 

 Summer Hill Quarry in the county of Meath. A fragment (cast) measures 52 mm. 

 from the centre of the umbilical cavity to a point near but not at the periphery ; 

 this represents a specimen which may have measured as much as 80 mm. in diameter. 

 It comes from the same county as the other, from near Trim. 



Localities. — Loughshinny, county of Dublin (No. N. 4299; V. 4301); Summer 

 Hill and near Trim (No. 37 K), county of Meath; Killorglin, county of Kerry 

 (Dingle Bay) (No. 3804 C). 



Sub-genus Muensterooebas, 1 Hyatt, L883. 

 G-lyphiocekas (Muenstei.mh'ki.'as) ckassum, sp. nov. Plate XLII, figs. 10 a — c. 



Description. — Shell of medium size, discoid, thick, somewhat compressed, the 



greatest thickness at the umbilical margin, rather more than two-tit'ths of the 



diameter of the shell ; height of the outer whorl aboul t hree-fift lis of the diameter 



1 F<u- definition <>t' this sub-genus see Appendix, p. 219. 



