126 DEVONIAN FAUNA. 



0. lineatum, Hisinger, is given by Portlock' as a synonym of 0. tenuistriatus, 

 Miinster; Portlock's species, however, is very much more coarsely ribbed than is 

 the present form, while that species as figured by Blake^ is of a much less regular 

 conoidal shape (being more dagger-like). 



Blake separates Portlock's species, or rather a portion of it having finer ribs, 

 from that of Miinster because the latter is stated to have a thick shell, whereas in 

 the former it is thin. The test of ours appears thick, but is somewhat confused 

 with the matrix. It appears to me, however, that unless this distinction be well 

 marked, which is not proved, it might easily be accounted for on other than specific 

 grounds, and the other reason Blake gives, the difference in geological age, is in 

 itself no reason for separating them. As, therefore, in his so-termed variety the 

 number of rays are the same, and the shape of the figured fragment agrees, it 

 must be regarded as a possible synonym pending further evidence, especially as 

 it occurs in the Wenlock as well as in the Bala beds. Barrande^ describes some 

 Swedish examples of 0. lineatum, Hisinger, which are very much larger than the 

 English fossil. These taper much less rapidly, and have rather deep chambers. 

 The ornamentation, which appears to be much the same in character, is just 

 visible to the naked eye, but this may perhaps not indicate that it is coarser, as the 

 size of the specimens is so much greater. On the whole, it appears most probable 

 that, in spite of the apparent resemblances, Miinster's fossil will prove to be 

 distinct from those of the latter authors. 



4. Oethoceeas Robbetsii, n. sp. PI. XIII, figs. 10 — 13. 



Cf. 1840. Oethocebas ieeegulaee, Miinster. Beitr., pt. 3, p. 99, pi. xix, fig. 11. 



Descri])tion. — Shell straight, very elongate, large, tapering at the rate of 

 about 1 : 13. Section circular. Septa very concave, hardly if at all oblique, 

 distant about one-third of their width. Syphon very large, about one-eighth the 

 width of shell, definitely constricted by the septa, but cylindrical or even slightly 

 narrower between them. External layer of shell very thin or papyraceous, and of 

 a black colour. Surface marked with multitudinous, rather irregular, fine, and 

 slightly arching transverse lines, about \ mm. apart, a few of which are slightly 

 larger than the rest, the irregularity being in some specimens excessive, owing to 

 injury or imperfection of formation, and there being occasionally extremely indis- 

 tinct, longitudinal inequalities, and a slight tendency in the rings to become 



^ 1843, Portlock, ' Rep. Greol. Londonderry,' p. 370, pi. xxvii, figs. 3 a, i ; and pi. xxviii, fig. 1. 



2 1882, Blake, ' Men. Brit. Foss. Ceph.,' pt. 1, p. 128, pi. vii, figs. 2, 11. 



2 1870, Barrande, ' Syst. Sil. Boheme,' vol. ii, pt. 3, p. 704, pi. ccccxxxviii, figs. 1 — 5. 



