128 DEVONIAN FAUNA. 



There is a close approach in its ornamentation to the specimens of 0. 

 suhannulare, Miinst., from Wolborough, from which it differs in the absence of 

 raised rings. 



0. Dannenbergi, d'Arch. and de Vern.,^ has decidedly narrower chambers, the 

 septa being distant less than a quarter, instead of more than a third, of their width. 

 It is not very easy to say whether the strige of ours are oblique to the septa as in 

 that shell. Sandberger describes the same species under the name 0. undato- 

 lineolatum, Sandb.,^ and there the shell is seen to be much more tapering, and the 

 concentric striae are much more regular and have a second series of minor 

 strigs, which are moreover clearly shown on a German specimen of that shell in 

 the British Museum. 



In 0. vittahim, Sandb.,' the strige are much finer and perfectly regular and 

 equal, and their curvature also seems different. 



In 0. crassum, F. A. Romer,* the strias seem more oblique and the chambers 

 are much narrower. 



In 0. Modreense, Sow., as given by F. A. Romer,^ the strijB are more regular 

 and sharper, and are more defined. As the width of the chambers is not seen, the 

 question of its identity cannot be settled from F. A. Romer's first work, and 

 Sowerby's original figure^ does not help. It looks somewhat angulated in section. 

 There are, however, some fine specimens in the British Museum which show that 

 the strige are much fewer and more distant, and that the shape of the shell is 

 quite different, being short and irregularly lumpy. Romer'' afterwards refigured 

 his shell, identifying it with the 0. lineare of Miinster and Sandberger. As 

 thus shown, it differs from ours in having much more distant septa. 



In 0. virgo, Giebel,^ the septa are far more distant. 



The section figured by Portlock as 0. maximum, Miinst.,^ agrees with that of 

 our shell, but this can only give generic identification. 



0. pendens, Blake,^° increases much more rapidly. 



0. expansum, Blake,^^ has the strige more undulating, and 0. argus^^ and 



1 1842, D'Arch. and de Vern., ' Geol. Trans.,' ser. 2, vol. vi, p. 345, pi. x.\viii, figs. 1, la. 



2 1852 ? Sandberger, ' Verst. Ehein. Nassau,' p. 163, pi. xviii, figs. 6 a — d. 

 ^ Ibid., p. 165, pi. XX, figs. 9 a, b. 



* 1843, F. A. Eomer, ' Verst. Harz.,' p. 35, i^l. x, fig. 6. 



5 Ibid., p. 36, pi. X, fig. 11. 



6 Sow. in Murch. ' Sil. Syst.,' p. 616, pi. vi, fig. 11. 



"^ 1850, F. A. Eomer, ' Beitriige,' pt. 1, p. 17, pi. iii, fig. 23. 

 8 1858, Giebel, ' Sil. Faun. Unterharz.,' p. 16, pi. iii, fig. 2. 



* 1843, Portlock, ' Eept. Geol. Londonderry,' p. 472, pi. xxxv, fig. 3. 



10 1882, Blake, 'Mon. Brit. Foss. Ceph.,' pt. 1, p. 122, pi. xi, figs. 2, 5. 



11 1882, Blake, 'Mon. Brit. Foss. Ceph.,' pt. 1, p. 118, pi. vi, fig. 15. 



12 1868, Barrande, ' Syst. Sil. Boheme,' vol. ii, pt. 3, p. 476, pi. cccxxv, figs. 1—18, &c., Et. F. 



