GLYPHI0CERA8 (BP]Y1UC11()CERAS) TRUNCATmr. ir,7 



tion, casts sometimes exhibiting them. The shell is for the most part, however, 

 (juite smooth. 



lJiiin'iisi<iii!>. 



Specimons in the Museum of Scieuce ami Art, Duliliii. 

 Geol. Surv. Coll. Lisnakorry General Coll. 



(No. 412-1). Clane. 



Diameter of shell . . . 112 mm. . 90 mm. 



„ \uiibilicus (edge to edge) . 20 ,, . 17 ,, 



,, ,, (sutm-e to suture) 15 ,, . 13 ,, 



Height of outer whorl . . 55 ,, . 46 ,, 



,, above preceding whorl (about) . 2!) ,, (aliout) 20 ,, 



Thickness of shell at umbilical margin . 3'.' ,, ,, 30 ,, 



These dimensions bring out very clearly the fiutness of the shell in this species, 

 its most conspicuous feature, and the one by which it is most easily recognised. 



Ajfiiiith'/i. — It is quite evident that this species is closely connected with the one 

 described under the name of GhjpMoci'rKs {Bri/rirltocemti) Hiibtruiicatnin (p. 168). 

 It differs from this in being flatter in form and in the possession of a smaller uniljili- 

 cus ; the truncation of the periphei'y appeal's to be equally strongly marked in the 

 two species, and to vary in degree in different individuals. The surface markings 

 are the same in both species, the distinctness of the transverse lines depending very 

 much upon the state of preservation of the shell. Under favourable conditions they 

 constitute in the present species a fairly distinct ornamentation. The constrictions 

 do not in any case constitute a remarkable feature, except in some very young 

 individuals ; they are only seen upon the cast, as the test completely covers them. 

 Taking the character of the suture-line into account, it ajipears that the chambers 

 are somewhat shallower in G. (£?.) truiicufiini than they are in G. (B.) sithtrancdtiun. 



licmarkx. — The l>rief description of this species given by Phillips runs as 

 follows : — " Very depres;5ed, back (in adults) truncate ; umbilicus open ; fine trans- 

 verse bent stria?." The type specimen being preserved (" Grilbertson Collection," 

 British Museum), the identity of the species was secured, though the feature upon 

 which the author founded it, the truncation of the periphery, is not always so con- 

 spicuous as it might l)e judged to be according to PhiUips's figure (' Geol. Yorks.,' 

 pi. xxix, fig. 21). Among the specimens before me the distinctness of tlie peri- 

 pheral flattening varies in different individuals, and while in some it is (piite 

 apparent in others it is scarcely discernible. This variability, however, does not 

 deprive the species of its individuality, its compressed form, as already stated, 

 supplying the principal specific feature. 



Glyphiocems [Dcuviclioceras) trKticntmn is one of the most common and most 

 widely distrilnited of the Carboniferous Goniatites in Ireland ; it varies consideral)ly 

 in size, and to some extent in thickness, some individuals being much more com- 



