118 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



ones may be traced in the genus Trigonoceras (through its two species, T. para- 

 doxicum and T. aigoceras ; the one coiled only in the earlier stages of the young 

 shell, the other evolute), and the more or less closely coiled (involute) shells 

 represented in the genera GmlonautUus, Apheleceras, and others of their tribe. 

 Locality, — Clane, county of Kildare.^ 



Genus Acanthonautilus, Foord, 1896. 



AcANTHONATJTiLUs BispiNOsus, A. H. Foovd. Plate XXVIII, fig. 1 ; Plate XXIX, 



fig. 1. 



189G. Acanthonautilus bispinosus, A. H. Foord. Ueber die Orthoceren des 



Kohlenkalks (Carboniferous Lime- 

 stone) von Irland. . . Inaugural-Dis- 

 sertation zur Erlaugung der Doktor- 

 wiirde . . . der Kg), bayer. Ludwig- 

 Maximilians-TTniversitat zu Miinchen, 

 p. 42. 

 1897. — ^ A. H. Foord. Geological Magazine, New 



Series, decade 4, vol. ix, p. 147, pi. vi ; 

 also J. P. Blake, ibid., p. 287. 

 1900. — [bispinosus], A. Hyatt. In tbe translation of 



Karl A. von Zittel's Text-book 

 [Grundziige] of Palaeontology, 

 edited by Charles P. Ea!5tman,^ 

 p. 525. 



Description. — Shell of medium size, nautikis-like in its general habit, some- 

 what globose, and expanding rapidly ; consisting of about two or two and a half 

 volutions, the inner ones concealed by the lateral expansion of the shell. Tbe 

 peripheral area is broadly rounded and somewhat flattened on the body-chamber, 

 especially towards the aperture in the adult, but more narrowly and evenly 

 rounded in the younger stages of growth. The umbilicus is rather large and very 

 distinctly funnel-shaped. It is provided with a thick and very conspicuous rim, 

 which is produced into long, flat, hollow, spine-like processes, projecting almost 

 at right angles to the longitudinal axis of tbe shell on each side of it. The spines, 



1 A small, remarkably well-preserved specimen of this species is contained in the British 

 Museum. 



2 With the exception of a few introductory pages, the whole of the class Cephalopoda in this 

 work has been revised and in great part rewritten by Professor Hyatt, who has introduced a new 

 classification for the larger groups, and many new genera. He has also added a very copious and 

 useful bibliography. 



