152 DEVONIAN FAUNA. 



Romer/ has a very elliptic section, and its siphuncle is situated very near its 

 ventral side. 



There is no reason for following Portlock^ in supposing that Phillips's shell 

 may be the same as 0. sub-fiexuosum, Mimster. 0. vagans, Salter,^ is distinguished 

 by having very distant unequal septa, varying in height from half to twice the 

 diameter of the shell. 0. gregarium, Sowerby,* has horizontal septa. 



0. aff. Marcellense, Vanux., is a species figured by Tschernyschew,^ which differs 

 from the present shell by having very much narrower, straighter chambers, and a 

 less central siphuncle. 



16. Orthoceeas, cf. 0. acdminatum, Eich'wald. PI. XII, figs. 5 — 7. 



? ? 1841 Oethoceeas Litdense, Phil, (not Sowerhy). Pal. Foss., p. 110, pi. xlii, 



figs. 206 a, b, c. 

 ? 1860. — ACTTMINATUM, EichwaM. Leth. Eossica, vol. i, p. 1215, pi. xlix, 



fig. 6. 



Description. — Shell large, rather rapidly tapering. Septa deeply but unequally 

 concave, oblique, and arching, rather narrow. Ratio of tapering 1 in 9. Section 

 elliptic, in the ratio of 10 : 12. Siphuncle somewhat excentric on the smaller 

 diameter. Surface nearly smooth, only marked by some indistinct, transverse, 

 coarse inequalities. Structure massive. 



Size. — 48 mm. in width. 



Locality. — Lummaton. Two fragmentary specimens of the body-chamber in 

 my Collection, and a third in the Woodwardian Museum. 



Bemarhs. — This species presents some points of agreement with that described 

 by Phillips, from Marwood and South-Petherwin, as 0. Ludense, Sowerby. It 

 approaches it in size, and the convexity of its septa is the same ; but its siphuncle 

 is much smaller, its section is less elliptic, and its shape is decidedly less conical, 

 as in that shell the rate of tapering amounts to 1 : 5. There are also other points 

 in which there are indications that more perfect specimens would show diver- 

 gencies from Phillips's description, and therefore it seems very unlikely that it 

 belongs to that species. The specimens, however, that I know of it are too frag- 

 mentary to allow a positive identification, and indeed it is not certain that 



1 1850, F. A. Eomer, ' Beitr.,' pt. 1, p. 50, pi. viii, figs. 8 a, b. 



2 1843, Portlock, ' Eept. Geol. Londonderry,' p. 372, pi. xxviii, fig. 3. 



3 1848, Salter, ' Quart. Journ. Geol. Soc.,' vol. v, p. 153, pi. vi, fig. 6. 

 * 1839, Sowerby in Murch., ' Sil. Syst.,' p. 619, pi. viii. fig. 16. 



5 1887, Tschernyschew, 'Mem. Com. Geol.,' vol. iii, pt. 3, p. 163, pi. iii, figs. 2 a—c. 



