166 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



1883. Munsteroceras truncatum, A. Hyatt. Pruc. Boston Soc. Nat. Hist., 



vol. xxii, p. 326. 



1888. Goniatites truncatus, B. Etheridge. Brit. Foss., vol. i, Palaeozoic, p. 313. 



1889. Glyphioceras truncatum, E. Holzapfel. Palseont. Abhandl., Dames uud 



Kayser, vol. v, i, p. 26, pi. i, figs. 8, 9. 



1890. Muensteroceras truncatum, G. Steinmann und L. Dbderlein. Eleniente 



der Palaeontologie, pt. 2, p. 393. 

 1895. Goniatites truncatus, G. H. Morton. Proc. Liverpool Nat. Field Club 



for 1894, p. 24. 



1897. Glyphioceras truncatum, A. H. Foord and G. C. Crick. Cat. Foss. 



Ceph. British Museum, pt. 3, p. 175, 

 fig. 82 (suture-line). 



1898. G. C. Crick. Trans. Linn. Soc, ser. 2, vol. vii, 



p. 108, pi. xx, fig. 19. 

 1900-1901. Goniatites truncatus, G. H. Morton. "The Carboniferous Limestone of 



Anglesey," Proc. Liverpool 

 Geol. Soc, p. 52. 

 1903. Glyphioceras truncatum, Wheelton Hind. Brit. Assoc. Adv. Sci., Bel- 

 fast, 1902, p. 215 : " Life-zones 

 in the Carboniferous Rocks." 

 [Not 1854 Goniatites truncatus, F. A. Boemer, Palteontograplrica, vol. iii, p. 94, pi. xiii, fig. 30. — 

 1884. Glyphioceras truncatum, A. Hyatt, Proc. Boston Soc. Nat. Hist., vol. xxii, p. 329.] 



Description. — Shell attaining a considerable size, much compressed, discoidal, 

 involute ; the greatest thickness at about one-third of the height of the whorl from 

 the edge of the umbilicus, rather more than one-third of the diameter of the shell ; 

 height of outer whorl three-fifths of the diameter of the shell. Whorls from five to 

 six ; inclusion nearly complete ; umbilicus small, shallow, from one-seventh to one- 

 ninth of the diameter of the shell in width. Whorl subquadrangular in section, 

 about one-third higher than wide ; indented to nearly one-third of its height by the 

 preceding whorl. Periphery more or less flattened or subtruncate, sometimes with 

 perceptible subangular margins ; sides very slightly convex, flattened ; umbilical 

 zone scarcely distinguishable, gently rounded, merging into the sides of the shell. 

 Body-chamber occupying rather more than a complete whorl ; aperture with a deep 

 lateral, and a deep peripheral sinus. Chambers rather deep, eleven or twelve in a 

 whorl; suture-line as in PI. XLIV, fig. 2 c, and PI. XLIX, fig. 14. 



Test thin, with fine sigmoidal lines of growth which become obsolete in large adult 

 specimens. A few constrictions, sometimes strong, sometimes feeble, are present in 

 all stages of growth (PL XLIII, fig. 5 ; PI. XLIV) ; these are broad and shallow, and 

 occur apparently at irregular intervals ; they are very conspicuous upon the cast, 

 hut are scarcely seen upon the test, which seems to fill them up almost entirely. In 

 a very large adult shell, the surface of which is much eroded, there are obscure 

 transverse folds near the aperture representing the lines of growth, and these are 

 seen in other specimens, large and small, under favourable conditions of preserva- 



