2 CARBONIFEROUS CEPHALOPODA OP IRELAND. 



can only be seen when the test has been removed. The edge of the aperture is 

 preserved in one place. Septa somewhat oblique, crowded together in the 

 younger part of the shell, making the chambers here very shallow, their depth 

 being less than one-fifth of their diameter. Nearer the body- chamber, however, 

 the septa rapidly widen their distance, so that within a space of 75 mm. their 

 distance apart is nearly doubled. Siphuncle, as determined by the necks of 

 the septa, lies at a distance of about three-eighths across the diameter of the 

 shell, probably cylindrical ; the tube itself has, however, been destroyed by 

 crystallisation within the chambers, which are filled with crystalline calcite. 

 Test rather thick, especially that of the body-chamber ; its surface marked 

 with obscure lines of growth, which are more conspicuous upon the body- 

 chamber than upon the rest of the shell. The shell may, nevertheless, be 

 regarded as essentially smooth. 



8h:e. — Length of the largest specimen 347 mm., but a considerable part of 

 the apical end is broken ofi". Greatest diameter 62 mm., least 30 mm. 



Affinities. — A comparison between this species and Orthoceras variahile is made 

 under the description of the latter, but I am not acquainted with any other 

 species with which it may be compared. 



Bemarhs. — The most noteworthy feature in this species is the rajjid transition 

 from the closeness of the septa in the apical and central parts of the shell to their 

 wide separation towards the body-chamber. 



LocaUtij. — Clane, county of Kildare. 



Orthoceras variabile, A. H. Foord. Plate I, figs. 2 a — d. 



1S96. Oethoceeas tauiabile, A. H. Foord. Ueber die Orthoceren des Kohlen- 

 kalks (Carboniferous Limestone) vou Irland. 

 . . . Inaugural-Dissertation zur Erlangung 

 der Doktorwiirde . . . der Kgl. bayer. 

 Ludwig-Maximilians-Universitat zu Miincheni 

 p. 19. 



Description. — Shell moderately elongate, tapering at the rate of 1 : C. Section 

 elliptic, the ratio of the two diameters as 11 : 9. Body-chamber slightly inflated, 

 the apertural end not preserved ; therefore its length relative to that of the entire 

 shell cannot be computed. Septa extremely numerous in the apical and central 

 portions of the shell, gradually increasing in width apart until the body-chamber 

 is reached ; thus in a section of the shell measuring 15 mm. in diameter the septa 

 are only 3 mm. apart, and where the diameter has increased to 30 mm. they 



