124 DEVONIAN PAUNA. 



tendency to become dotty near tlie apex. Blake^ distinguishes Barrande's 

 0. originale from Miinster's shell, pointing out the curious formation of its test, 

 which is quite unlike that of the present species. 0. spedandum, Barrande,^ has 

 these rays still stronger and fewer and not alternate, and the surfaces between 

 them closely barred. It presents no signs of transverse folds, and the tube is 

 slightly recurved. 0. virgatum, Sowerby,^ from the Aymestry Limestone, has these 

 rays still fewer and coarser, has transverse constrictions, and diminishes very 

 rapidly and irregularly towards the apex. 0. polygonum, Sandberger,^ again has 

 these longitudinal ribs much larger and stouter. 0. lineatum, Hisinger, as figured 

 by Portlock,^ has a somewhat similar ornamentation, but Miinster's® figures of his 

 0. tenuistriatum, which Portlock regards as a synonym, and Hisinger's own 

 figures,'^ are very difierent from our specimens. Their longitudinal markings are 

 much finer, and they show no transverse ornamentation. 



0. coralliforme, M'Coy,^ seems similar in its minor ornament, but it has many 

 fewer rays. 0. electum, Barrande," again has fewer rays, and its fine transverse 

 imbrications are more regular and undulating, while there is an absence of the 

 irregular transverse foldings, and the shell is slightly recurved. 0. Jonesii, 

 Barrande,^° has closer, broader rays, and more regular and oblique transverse strias. 

 0. Bacchus,^^ Barrande, has fewer major rays, more strongly marked and numerous 

 minor rays, no signs of transverse undulations, and a slight curvature. 



3. Orthoceras tenuistriatum, Milnster. PI. XIII, figs. 2, 2 a, 2 b. 



1840. Oethoceeatites tenuistbiatus, Miinsi. Beitr., pt. 3, p. 102, pi. xx, 



figs. 4, 4 a. 

 ? 1843. Orthoceeas tenuistriatum, PortlocTc. Geol. Rep. Londonderry, p. 370 



(pi. xxviii, fig. 1 ?). 

 ? 1852. — — M'Coy. Brit. Pal. Foss., p. 317. 



1 1882, Blake, ' Mon. Brit. Foss. Cepb.,' pt. 1, p. 110, pi. vii, figs. 5, 10. 



2 1868, Barrande, ' Syst. Sil. Boheme,' vol. i, pt. 3, p. 223, pi. cclxvi, figs. 5—17, £t. G ? and E. 

 8 1839, Sowerby in Murch., ' Sil. Syst.,' p. 620, pi. ix, fig. 4. 



* 1852 ? Sandberger, ' Verst. Ehein. Nassau,' p. 162, pi. xx, figs. 1 a — c. 



'•' 1843, Portlock, ' Eept. Geol. Londonderry,' p. 370, pi. xxvii, figs. Za,b; pi. xxviii, fig. 1. 



« 1840, Miinster, ' Beitr.,' pt. 3, p. 102, pi. xx, figs. 4, 4 a, 4 h. 



^ 1837, Hisinger, ' Leth. Suec.,' p. 29, pi. ix, fig. 6. 



8 1846, M'Coy, ' Syn. Foss. Sil. Irel.,' p. 8, pi. i, fig. 3. 



9 1868, Barrande, ' Syst. Sil. Boheme,' vol. i, pt. 3, p. 243 ; pi. cclx, figs. 1—27, and pi. ccclxii, 

 figs. 1—3, Et. E. 



10 Ibid., p. 200, pi. ccliii, figs. 1—7; pi. cecciv, figs. 10, 11, and pi. ccccliii, figs. 3—7, Et. E. 



" 1866, Ibid., p. 237, pi. ccxiii, figs. 10-13 ; pi. cclxx, figs. 1—16 ; and pi. cclxxi, figs. 1—21, ^t. E. 



