572 BRITISH PALZZOZOIC FOSSILS. [CepHaLopopa. 
This species is distinguished from the O. cylindracewm by the greater number of chambers in a space equal 
to the diameter at the same size. Mr Phillips's name and description indicate a disproportionately great 
distance between the septa of the young shell; but his figure, and the still younger specimens which I have 
examined, agree in having five septa to a diameter in the larger specimens throughout, and four, or slightly less, 
in a diameter when so small as two lines in diameter. The section is more nearly circular than in the O. ovale, 
and the septa much more numerous in a given space, at a given diameter. 
Position and Locality—Rare in the carboniferous limestone of Lowick, Northumberland; rare in the 
carboniferous limestone of the Isle of Man. 
OrTHOCERAS (Loxoceras) LATERALE (Phill.) 
Ref. and Syn.—Phill. Geol. York. Vol. IT. t. 21. f. 8; Pal. Foss. f. 205a (not ¢); =O. subimbricatum Portk. 
Geol. Rep. p. 391. (not O. wndulatum Sow. Min. Con.). 
Desc.—Gradually tapering (at the rate of one and half lines in an inch, from five lines to two inches in 
diameter) ; section very broad, oval; septa moderately numerous (four in a diameter at half inch, and six to 
seven at one and half to one and three-fourths of an inch in diameter, eight in adult diameter of two and half 
inches), oblique, slightly sigmoid on the sides, crossing the anterior face with a very slight forward convexity, 
and crossing the opposite face with a stronger backward wave on their posterior edge; siphon on, or nearly on 
the conjugate or smaller axis, a little eccentric (about half its diameter from the centre); surface crossed by fine, 
imbricating, slightly irregular strize (six in the space of one line); last chamber with a narrow constriction a 
little behind the edge of the mouth. 
This large species tapers more gradually than the O. Breynii, to which it is allied, and has the wave on the 
more posterior edge of the septa less strongly marked ; it is also closely allied to the O. wadulatum of Sowerby, 
with which Phillips supposed it identical, but from which Col. Portlock distinguished it by the very tangible 
characters of the much less approximate septa at a given size, and the more nearly central siphon. 
Position and Locality.—Rare in the carboniferous limestone of Derbyshire; not uncommon in the carboni- 
ferous limestone of Lowick, Northumberland; rare in the carboniferous limestone of Kendal, Westmoreland. 
ORTHOCERAS OVALE (Phill.) 
Ref.—Phill. Geol. York. Vol. II. p. 238; M. V. K. Geol. Russ. t. 25. f. 1. 
Desc.—Very gradually tapering ; section very broad, oval, or almost circular; septa with simple edges, 
and a scarcely perceptible obliquity ; siphon moderately large, almost central, or less than half its diameter 
eccentric towards the most posterior edge of the septa; shell thick; surface nearly smooth, crossed by very 
minute, close, slightly flexuous striae of growth (twenty-six in a space of one line) under the lens. A specimen 
one inch three lines in diameter at large end, and three inches long, is one inch in diameter at the smaller 
broken end (two and half inches being occupied by the last chamber) ; there are three interseptal spaces in a 
diameter when it equals eleven lines, and the same number in a diameter when the latter is five lines. 
This species is distinguished from the O. inequiseptum and other allied forms by the greater distance which 
the septa are apart at any given size. There is a strong constriction about half an inch wide, at one-third the 
length of the last chamber from its anterior edge. The description in the Geology of Russia is correct, but the 
figure places the siphon too far from the centre; according to that work also there are rather less than three 
interseptal spaces in a diameter when that equals eight millemetres (or about four lines). The O. affine of 
Portk. (Geol. Rep. t. 27. f. 9) seems to belong to the same species. 
Position and Locality—Not uncommon in the carboniferous limestone of Poolwash, Isle of Man; ear- 
boniferous limestone of Molerstang. 
