132 DEVONIAN FAUNA. 



0. Maclareni, Salter, as given by Blake,^ lias larger and coarser ribs with less 

 defined interspaces. 



0. argus, Barrande,^ and 0. capillosum, Barrande,^ have very much finer 

 lineations. 



6. Orthoceras ViCARii, var. eductdm. PI. XIII, fig. 8. 



Two or three of the small specimens which I have collected from Lummaton, 

 differ from the species described above in the much greater comparative distance 

 of the transverse rings, and in being almost perfectly cylindrical. These rings 

 are half their diameter apart, instead of, as in the generality of the larger speci- 

 mens, being separated by only about one tenth the width of their diameter. We 

 have seen, however, that the species varies considerably in these particulars ; and 

 as in the figured specimen of the present variety the distance of the rings varies 

 considerably in different parts of the shell, there is no reason for regarding these 

 points as of specific importance. In all probability the present specimens are 

 either very young animals or a dwarfed form of the present species. 



Locality. — Lummaton. 



Affinities. — 0. pauper, Barrande,* seems very similar, but the ribs seem closer 

 and stouter, and facing upwards instead of having equal slopes. 



7. Orthoceras dolatum, Whidborne. PI. XIV, figs. 1 — 3. 



1852 ? Oethoceeas tubicinella, Sandlerger (not Sowerly'). Verst. Ehein. 



Nassau, p. 169, pi. xix, figs. 6 a — d. 

 1889. — HASTATUM, WMdbome. Geol. Mag., dec. 3, vol. vi, p. 29. 



Description. — Shell large, straight, conical, slowly but definitely tapering at 

 the rate of 1 mm. in width to about 9 mm. in length. Septa concave, rather 

 narrow, oblique. Siphuncle sub-central, large. Section elliptic. Surface bearing 

 low, broad, rounded, and very oblique rings of about the same size as the inter- 



1 1882, Blake, ' Mon. Brit. Foss. Ceph.,' pt. 1, p. 105, pi. vi, figs. 7-10. 



2 1868, Barrande, ' Syst. Sil. Boh^me,' pt. 3, p. 476, pi. cccxxv, figs. 1—18, &c., Et. F. 



3 Ibid., p. 486, pi. cccxxv, figa. 19—33 ; pi. ccclvii, figs. 4 — 7 ; and pi. cccxciv, figs. 16—19, 

 Et. E— H. 



* Ibid., vol. i, p. 340, pi. cclvii, figa. 10—13, Et. E. 



