ORTHOCERAS COLEI. 3 



are 5 mm. distant, while the last two septa are separated by an interval of 10 mm. 

 The septa, as seen in a longitudinal section, are somewhat displaced by mineral- 

 isation, but they preserve on the whole their normal form. Siphuncle excentric 

 by about its own diameter; cylindrical, rather wide. Test smooth. 



Size. — Length of the largest specimen about 360 mm. Diameter of the base 

 of the body-chamber 55 mm., that of the apex 12 mm. 



Affinities. — This species is evidently related to Ortlwceras Leinsterense, from 

 which, however, it differs in its higher rate of tapering and closer septa. In its 

 very numerous septa it is comparable also with Ortlwceras princeps, de Koninck, 

 but the latter has a much more rapidly tapering shell, and more evenly spaced 

 septa. 



Remarks. — This beautiful species appears to be rare ; I have met with only two 

 or three examples of it. The most marked feature in it consists of the very 

 numerous septa, which greatly exceed in number those of most species of Orthoceras 

 of this size. Their original structure has been considerably modified by crystal- 

 lisation ; the necks of the septa are often pushed out of place, as in the example 

 figured, which only shows a small portion of the siphuncle proceeding downwards 

 from the penultimate septum. 



Locality. — Clane, county of Kildare. 



Orthoceras Colei, A. H. Foord. Plate II, figs. 1 a — c. 



1S9G. Ohthoceras Colei, A. H. Foord. Ueber die Orthoceren des Kohlen- 



kalks (Carboniferous Limestone) von Irland. . . 

 . Inaugural-Dissertation zur Erlangung der Dok- 

 torwiirde . . . der Kgl. bayer. Ludwig- 

 Maximilians-Universitat zu Miinchen, p. 18. 



Description. — Shell elongate, tapering at the rate of about 1 : 6. Section 

 normally circular, but elliptic by pressure, as is proved by the distortion of the 

 septa at the sides (PL II, fig. lb). Body-chamber about 155 mm. in length 

 in a specimen measuring about 600 mm., or about one-fourth of the whole length 

 of the shell. 1 There is a well-marked constriction on the cast below the aperture, 

 which constriction is as usual covered by a thickening of the test when the latter 

 is present. Septa very deeply concave, distant from each other about one-third 

 of the longer uncompressed diameter of the shell. Siphuncle cylindrical, wide, 

 being from one-eighth to one-ninth of the diameter of the shell near the body- 



1 The specimen is preserved nearly to the apical point, but there is an intermediate piece lost 

 which must have measured about 80 mm. ; this has been added in computing the total length. 



