CrpHaLopopa. | LOWER PALAZOZOIC MOLLUSCA. 319 
OrTHOCERAS (Cycloceras) ANNULATUM (Sow. Sp.) 
Ref. and Syn. = Orthoceras Id. Sil. Syst. t. 9. f. 5; and Min. Con. t. 133 
=? Orthoceras undulatum His. Leth. Suec. t. 10. f. 2. 
Sp. Ch.—Shell tapering at the rate of three lines in two inches; section broad-oval ; siphon large, between 
the centre and one of the broad sides ; rings obtusely angular, prominent, slightly oblique, three in half an inch, 
at a diameter of nine lines, four in the same space, at a diameter of six lines, two in the same space ata 
diameter of one inch three lines, four lines apart, at a diameter of two inches; interannular spaces deep, 
concave, marked with six or seven transverse, imbricating striee, bent downwards into numerous wayes, about a 
line wide, through which sometimes pass indistinct longitudinal ridges from one to two lines apart. 
The longitudinal ridges of this species are rarely well marked, they pass through the obtuse parts of the 
undulations of the transverse striz. The siphon seems rather nearer the side than in Sowerby’s figure, (Min. 
Con.), which I have no doubt, however, from the striation of the lower part of the right-hand figure, represents 
an extremely smooth example of the same species. 
Position and Locality—Common in the Woolhope limestone of old Radnor, Radnorshire; Wenlock 
limestone of Ledbury, Herefordshire ; calcareous Bala schists of Dermydd-fawr, under Craig Bronbanog, Denbigh- 
shire; Caradoc shale, Cheney Longville, Shropshire; Coniston (Upper Bala) limestone of Coniston, Lanca- 
shire. 
ORTHOCERAS (Cycloceras) ARCUOLIRATUM (Hall Sp.) 
Ref. and Syn. = Orthoceras arcuoliratum Hall, Pal. N. York, t. 42. f. 7. 
Sp. Ch.—Slender, very slowly tapering, apical angle about 10°; section circular, or very broad-oval ; 
siphon central; surface girt with very oblique obtuse rings, separated by concave spaces equalling them in 
width, the lowest or posterior point of each ring about two interannular spaces lower on the shell than the most 
anterior curve or opposite point of the same ring, at the opposite circumference ; four rings in the space of five 
lines in a specimen four lines in diameter ; traces of very close, fine, longitudinal striz. 
The fragment described is about two inches long, and only differs from the American species in a very 
slight, probably accidental, compression. 
Position and Locality —Rare in the limestone (Bala Group) of Wrae Quarry, Upper Tweed, near Broughton. 
ORTHOCERAS (Cycloceras) BILINEATUM (fall Sp.) 
Syn. = Orthoceras bilineatum Hall, Pal. N. Y. t. 43. f. 2 and 3. 
Gen. Char.—Tube rapidly tapering (at the rate of two lines in two inches), girt with large, slightly oblique, 
subangular rings touching each other, or separated by re-entering angular spaces, four rings in the space of half 
an inch, at the diameter of half an inch; surface marked with strong longitudinal striz, three or four in the space 
of one line, usually with one much finer line between each pair, the whole being crossed by microscopic transverse 
striz ; length of fragment, imperfect at each end, four and half inches, diameter at large end eight lines, 
This species is readily distinguished from the Cycloceras Ibex, by its much more rapidly tapering figure, 
coarser longitudinal striz, and proportionally much thicker subangular rings, nearly separated by the narrow 
re-entering angular spaces, formed by the meeting of their sides. The section in our specimen is very broad-oval, 
agreeing with Hall’s figure 3: according to that author the siphon is placed between the centre and the 
margin; the identity between our specimen and that of the American Trenton limestone is most perfect in all 
respects. 
Position and Locality—In the green Bala quartzite of Ardwell, S. of Girvan, Ayrshire. 
OrTHoceras (Cycloceras) Ipex (Sow.) 
Ref. and Syn. = Orthoceras Ibex Sow. Sil. Syst. t. 5. f. 31+ O. articulatum Id. id. f. 30. 
Sp. Ch.—Shell long, nearly cylindrical (tapering at the rate of about half a line in three inches at the 
