134 DEVONIAN PAUNA. 



tliese distinctions will be preserved when more numerous and perfect fossils are 

 discovered. Thus 0. dolatum differs from 0. tubimiella, in tapering more rapidly, 

 in having fewer, lower, more oblique and confluent ribs, stronger radiations, and 

 a more elliptic section. 0. sub-tuhicinella differs from 0. tubicinella in having 

 more numerous, less oblique and more defined ribs, and a circular section ; while 

 it becomes cylindrical about the body-chamber. Thus it differs from the present 

 species still more than does the latter shell. 



0. tubicinella, Sandberger^ (not Sowerby), difl'ers slightly in the number and 

 fineness of its longitudinal marks, and its circular section, but it probably belongs 

 to the species now under consideration. 



As Billings ^ had already used the name 0. hastatum for a Canadian species, it 

 has been necessary to change the name suggested in the ' Geological Magazine ' 

 for the present form. 



Affi7iities. — 0. dolatum appears to be very similar to Orthoceratites calamiteus, 

 Miinster,* but the swellings seem much narrower than in that species, and it has 

 no indications of fine transverse striae, while the longitudinal threads seem to be 

 much fewer and coarser. 



8. Oethocbkas tubicinella, Sowerby. PI. XIV, figs. 4, 4 a, 5, 6 a. 



1840. Oethoceeas tubicinella, Sow. Geol. Trans., ser. 2, vol. v, p. 703,* 



pi. Ivii, fig. 29. 



1841. — — FMl. Pal. Foss., p. 112, pi. xliii, fig. 211. 

 1843. — — var., Portlock. Eep. Geol. Londonderry, p. 367, 



pi. XXV, fig. 4. 

 ? 1843. — TUBICINELLA, var. SUBNODOSUM, Portloch. Eep. Geol. Lon- 



donderry, p. 367, pi. XXV, fig. 3. 

 ? 1843. — GBACILE, Fortlock (not Blumenbach) . Eep. Geol. London- 



derry, p. 366, pi. XXV, fig. 2. 

 1888. — TUBICINELLA, Etheridge. Foss. Brit., vol. i. Pal., p. 168. 



1888. — — Foord. Cat. Foss. Ceph. Brit. Mus., vol. i, p. 87. 



Description. — Shell elongate, large, slowly tapering. Rate of tapering about 1 

 in 12. Section slightly elliptic, the diameters being in the ratio of about 9 to 10. 

 Septa very concave, oblique, distant from each other between a fourth and a fifth 

 of their diameter. Surface ornamented with regular, prominent, transverse, 

 rounded and defined rings, considerably narrower than their interspaces, corre- 



^ 1853, Sandberger, ' Verst. Ehein. Nassau,' p. 169, pi. xix, fig. 6. 



2 1857, Billings, " Eeport of Progress," ' Geol. Surv. of Canada,' p. 333. 



2 1839, Miinster, ' Beitr.,' pt. 1, p. 59, pi. xvii, figs. 5 a, h. 



