68 CARBONIFEROUS CEPHALOPODA OE IRELAND. 



mucli thicker proportions, and transversely broader whorls. Nautilus Mosquensis, 

 Tzwet.aev ^ {= siihsulcatus, Trautschold, non Phillips) somewhat resembles the 

 present species, but the periphery is broader and not so concave, and the sutures 

 are not so sinuous. A. hibernicum, A. H. Foord and G. 0. Crick,^ is closely allied 

 to A. mutabUe, but differs from it in its less slender proportions, less deeply 

 channelled periphery, and in the non-contiguous condition of the first half-whorl. 



Bemarks. — In the ' Catalogue of Fossil Cephalopoda, British Museum,' pt. 2, 

 1891, p. 91, A. mutahile is included in the synonymy of a species described by J. 

 Sowerby under the name of Ellipsolites compressus.^ It was afterwards discovered, 

 however, by Mr. G. 0. Crick and the writer that Sowerby's species was identical 

 with the one described by that author as Ammonites Hensloivi,* and it was further 

 ascertained that Ellipsolites compressus ( = Ammonites Henslowi) was a Goniatite 

 belonging to the genus Prolecanites, Mojsisovics. This correction was published 

 with full details and illustrations of the species in the ' Geological Magazine' for 

 January, 1894, and subsequently in the' Cat. Foss. Ceph. British Museum,' pt. 3, 

 1897; this allusion to the subject will therefore be sufficient. 



Localities. — Rathfarnham, county of Dublin ; Clane and Naas, county of 

 Kildare ; Cregg, near Nobber, county of Meath ; Little Island, near Cork ; Rath- 

 keale, county of Limerick 



h. Aphelecebas HiBEt4NicuM, A. H. Foord and G. G. Griclc. Plate XXI, figs. 4 — 7. 



1893. DisciTES HiBEiiNicus, A. H. Foord and G. C. Crick. Geological Maga- 

 zine, dec. 3, vol. X, p. 251 (woodcut, p. 254). 



Description. — Shell discoid, compressed ; whorls three (in largest individual 

 measured), rather slowly increasing, the first half- whorl free, the rest in contact, 

 but leaving the sides of the inner whorls entirely exposed ; the impressed zone 

 faintly defined on the body-chamber. The latter occupies fully one-half of the 

 last whorl, and becomes free towards the aperture. Section of the whorl subcir- 

 cular in the young, but becoming truncated-cuneiform and tetragonal in the 

 adult. Umbilicus broad and shallow, with a large central vacuity ; its walls 

 sloping in such a degree as to form a very obtuse angle with the sides of the 

 shell. Periphery convex in the free portion, concave in the last whorl, about one- 

 half of the width of the side, exclusive of the umbilical slope; bounded on each 



1 ' Mem. Comite Geol. [Russia],' vol. v. No. 3, 1888, p. 52. 



* ' Geol. Mag.,' decade 3, 1893, vol. x, p. 251 (woodcut). 

 3 ' Mia. Conch.,' vol. i, 1813, p. 84, pi. xxxviii. 



* Ibid., vol. iii, 1820, p. Ill, pi. cclxii. 



