ORTHOCERAS. . 137 



in our shell the ribs are oblique, though not so much so as in Blake's figures. A 

 more distinctive character may be found in the greater acuteness and distance 

 of the longitudinal ribs ; but, where two species from such different formations and 

 so variable in themselves are evidently so closely allied, it is difficult to decide their 

 identity until their representative in the intermediate Upper Silurian can be traced. 

 It is to be noted that Blake's name of " 0. gracile, Portlock," will not hold good, as 

 that name had been already applied by Blumenbach to a very different shell. The 

 same species has, however, been described under the name of 0. annellatum by 

 M'Coy,^ and this name will therefore take its place. 0. Nicholianum, Blake,'' 

 from the Upper Silurian, agrees with ours in the sharpness of its rays, but 

 distinctly differs in the closeness of its septa. 



0. pulchrum, Barrande,^ is a very similar form ; but in it the ribs are more 

 rounded, lower, and broader than the interspaces, and the longitudinal rays are 

 much more numerous. 



0. Lorieri, d'Orbigny,* as given by Barrels,^ differs in being more cylindrical, 

 in its ribs being quite horizontal, and in its longitudinal threads being rather more 

 numerous, and without any intermediate series of lines. In Barrois' figures 

 very fin^ transverse striee are seen ; there is no clear evidence of the existence 

 of such strige in the English shell. 



9. Oethoceras sub-tubicinella, n. sp. Plate XIV, figs. 6, 6 a. 



Description. — Shell elongate, straight, tapering at the rate of 1 in 12 in the 

 septal part, but becoming almost cylindrical about the body-chamber. Section 

 circular. Siphuncle central. Septa only slightly oblique, deeply concave. Surface 

 bearing numerous, elevated, rounded rings about their own diameter apart ; about 

 six rings occupying a space equal to the width of the shell ; the whole covered by 

 about thirty strong, raised, thin rays, which do not alternate in the lower part of 

 the shell but have at the upper end a secondary series of much finer intermediary 

 lineations, three times as numerous as the major rays. 



Size. — A broken specimen measures 40 mm. in length by 13 in width. Another 

 specimen 78 mm. long, has a diameter of 22 mm. 



Locality. — Wolborough. One specimen is in the Battersby Collection in the 

 Torquay Museum, and another is in the Museum of Practical Greology. 



Bemarks. — I formerly regarded these fossils as specimens of 0. tubicinella, and 

 was led into some confusion thereby. Taking, however, the specimen in the 



1 1851, M'Coy, 'Brit. Assoc. Eep.,' p. 103. 



2 1882, Blake, ' Mon. Brit. Toss. Ceph.,' pt. 1, p. 89, pi. iii, figs. 7, 8, 15. 



3 1868, Barrande, ' Sil. Syst. Boheme,' vol. ii, pt. 3, p. 264, pi. cclxxvi, figs. 1—17, Et. F and G. 

 * 1819, D'Orbigny, ' Prodrome,' p. 55. 



5 1889, Barrois, ' Mem. Soc. Geol. Nord.,' vol. iii, ' Fauue Calc. d'Erbray,' p. 228, pi. xvi, figs. 4 a — c. 



