ORTIIOCERAS. 127 



foliaceous, as well as to be very slightly crenulated by the longitudinal marks. 

 The transverse marks equally well seen upon the inner shell. 



Size. — The largest specimen measures 35 mm. in width. 



Locality. — From Wolborough there are two finely preserved specimens in the 

 Museum of Practical Geology, and two in Mr. Vicary's Collection, only one of 

 which shows the transverse striation. From Lummaton there is one specimen in 

 my Collection. In the Torquay Museum is a fine and instructive specimen, which 

 probably came from Lummaton, but might have come from Wolborough. 



Bemarhs. — These shells seem to come very near to 0. cinctum, Sow.,^ as 

 figured and described by Miinster^ as well as the closely allied 0. linearis, Miinster,"'' 

 with neither of which, however, Mr. Roberts or myself think they can be identical, 

 on account of the inequality and irregularity of their striation, and because of 

 their septa being distant one-third of their width instead of one-fifth, as in the 

 Grerman shell. The original 0. cinctum is very vaguely described, but both 

 Sowerby's figure and description would point to the annuli being very much 

 fewer and coarser than they are in the fossils we are now considering. I think 

 also there cannot be a doubt that they are distinct from the 0. cinctum of Phillips* 

 from Devonshire, inasmuch as one of the type-specimens of that species shows 

 that the surface, of which it retains a fragment, is smooth. Phillips's Yorkshire 

 0. cinctum^ seems to belong to Sowerby's original species, and it differs from the 

 present species in the regular, undulating, and more defined character of its 

 annuli. 



Mr. Roberts and I consider that this species comes much nearer to 0. irregulare, 

 Miinst.,® but that still it is probably distinct from it, as in that species the 

 markings are much more irregular than in ours. Judging from its description, it 

 is the species which is most like it of any that I know ; but a doubtful specimen of 

 it in the British Museum is very distinct, having much fewer and more distant 

 impressed striae. 



From Sandberger's version of 0. lineare, Miinster, it diff'ers in its strise not 

 being equal and regular. Sandberger's figure, 7 c, of this shell,^ though it 

 approaches it almost exactly in ornamentation, has the septa very much closer 

 together. 



From 0. arcuatellum, Sandb.,^ it is distinguished by its much less conical figure 

 and its less undulating strise. 



1 1829, Sow., Min. Conch.,' p. 168, pi. dlxxxviii, fig. 3. 



2 1840, Miinster, ' Beitr.,' pt. 3, p. 99, pi. xix, fig. 4. ^ i]ji^^ p. 99^ p] xix, fig. 1. 

 * 1841, Phillips, ' Pal. Foss.,' p. 109, pi. xli, fig. 204. 



5 1836, Phillips, ' Geol. Yorks.,' pt. 2, p. 236, pi. xxi, fig. 1. 



6 Miinst., ' Beitr.,' pt. 3, p. 99, pi. xix, fig. 11. 



7 1852 ? Sandb., ' Verst. Rhein. Nassau,' p. 164, pi. xviii, figs. 7 a—c. 



8 Ibid., p. 166, pi. xix, figs. 2 a—^. 



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