136 DEVONIAN FAUNA. 



shape. 0. suhannulare, Miinster,^ lias the ribs closer and less defined, no longi- 

 tudinal threads, and regular coarse and parallel transverse marks, about nine 

 times as numerous as the ribs. 0. ibex, Sowerby,^ comes very close to the last- 

 mentioned species, but in it the transverse threads are very much finer and the 

 ribs smaller and more definite. In these two species the ornamentation merges 

 on the body-chamber into irregular parallel transverse lines. Lastly, of the 

 proximate forms of which there are examples in the British Museum, 0. pseudo- 

 caJamiteum, Quendst.,^ and Barrande,* has distant and direct ribs, few regular and 

 wall-like, lamellar longitudinal lines, and eight or nine indefinite, concentric, 

 transverse lineations between each rib. Though distinctly difierent from the 

 present form, it is closely allied to it, and appears to be its representative in the 

 Bohemian Rocks. 



0. nodulosum, Schlotheim, as figured by d'Archiac and de Verneuil,^ is very 

 different in its ornament. It has no longitudinal strise ; and the rings are broken 

 into rounded nodules. 



In Sandberger's figure (6 a) of his 0. tuhicinella,^ the transverse striae are repre- 

 sented as exceedingly fine, there being between twenty and thirty for each ring. 

 The indications in our specimens would lead to the supposition that in them the 

 striae were much fewer and coarser. Sandberger's figure differs, moreover, in the 

 indefiniteness and fewness of its rings, so that probably it should be referred to 

 0. dolatum rather than to the present species. 0. temiilineatuin, Sandberger,^ is 

 distinguished by the longitudinal striae being much finer and more numerous, the 

 rings being fewer and narrower, and the septa being, according to his description, 

 distant. 



In the report on the Geology of Londonderry, Portlock gives three species, 

 0. gracile, Blumenbach,^ 0. tubicinella, Sowerby, and 0. calamiteum, Miinster,^ all 

 of which Blake^" regards as one species, " 0. gracile, Portlock," differing from both 

 Sowerby's and Miinster's shells. Blake's shell appears to be a very variable species 

 and one which is very similar to 0. tiibicinella. The differences which Blake insists 

 upon, viz. more direct ribs and more regular and constant rays, neither hold well. 

 The former appearance seems due to the aspect of the figures drawn ; and certainly 



1 1840, Munster, ' Beitr.,' pt. 3, p. 99, pi. xix, fig. 3. 



3 1839, Sowerby in Murch., ' Sil. Syst.,' p. G13, pi. v, fig. 30. 



3 1852, Quenstedt, ' Handbuch Petref.,' p. 342, pi. xxvi, fig. 8. 



4 1868, Barrande, ' Syst. Sil. Boheme,' vol. ii,pt. 3, p. 261, pi. cclxxviii, figs. 1—33, &c., Et. E, F, G. 

 ^ 1842, D'Arcli. and de Vern , ' Geol. Trans.,' ser. 2, vol. vi, p. 347, pi. xxxi, figs. 4, 4 a. 



" 1852?, Sandberger, ' Verst. Ehein. Nat^sau,' p. 169, pi. xix, figs. 6 a — d. 

 "^ Ibid., p. 168, pi. xix, figs. 7, 7 a. 



^ 1803, Blumeubach, ' Specimen Archaeologise Telluris,' p. 21, pi. ii, fig. 6. 

 9 1839, Miinster, ' Beitr.,' pt. 1, p. 59, pi. xvii, figs. 5 a, h. 

 10 1882, Blake, ' Mon. Brit. Foss. Ceph.,' pt. 1, p. 85, pi. iii, figs. 5, 9. 



