316 BRITISH PALAZOZOIC FOSSILS. [CrrHALopopa. 
the joints of which instead of being cylindrical are globular, and having at the same diameter of the outer shell 
(one and half inch) three siphonal constrictions in the space occupied by two in the O. Brighti. Both species 
are usually found with the siphon well preserved, in a mass of calcareous spar, having the form of the outer 
shell, which with the septa has usually disappeared. 
Position and Locality.—W enlock limestone, Ledbury, Herefordshire. 
OrTHOCERAS PoLItuM (J/°Coy). PI. 1. L. fig. 30. 
Ref—Id. M°Coy, Ann. Nat. Hist. 2nd Series, Vol. VIT. p. 46. 
Sp. Ch.—Very elongate, conic, regularly tapering at the rate of half a line in one inch from a diameter of 
seven lines, from which size to five lines the septa have a uniform distance of three lines apart; they are 
slightly oblique, convex, with even edges; section nearly circular; siphon moderate, eccentric, its own 
diameter from the centre; surface smooth. 
One specimen with a glossy, horn-like external surface, slightly imperfect at each end, measures one inch 
four lines in diameter at the mouth, is one foot eight inches long, and measures two lines in diameter at the 
smaller end, where the septa are slightly oblique, and one and one-third lines apart. Its extremely slow rate 
of tapering and the regularity of the distant septa, separate it from the O. vagans (Salt.) 
Position and Locality—In the impure calcareous concretions (Bala rock) of Glenquaple, Ayrshire. 
Explanation of Figures—P1. 1. L. fig. 30, portion of posterior end of very large specimen, natural size ; 
30a, end view of a septum shewing form of section and position of siphon. 
ORTHOCERAS PRIMAVUM (forb. Sp.) 
Ref. and Syn. = Creseis primeva Forbes, Geol. Journ. Vol. I. p. 146. 
Sp. Ch—Very elongate, slender, apical angle about 6°; a nearly perfect specimen four and half inches 
long and pressed nearly flat has the chambered portion about two inches nine lines long, tapering to a point 
from a diameter (in compressed specimens) of three lines at the last septum, from which the last chamber 
rather abruptly widens to five lines (also compressed); surface smooth; septa very convex, about one line and 
half apart in the upper half of the chambered portion. 
This species when uncompressed is very slender, and does not exhibit the abrupt widening of the last 
chamber, usually seen where the chambered part has resisted the pressure. It seems to have more distant 
septa than the figure named by Sowerby (in Sil. Syst.) O. attenwatum, but of which no description is given, 
and of which he did not see the specimen, which however is stated to come from shales of the same age as the 
present fossil. The supposed longitudinal groove in the specimens I have seen, seemed to be only a crush in the 
last chamber. 
Position and Locality —Common in the black Upper Bala shale at Builth Bridge, Radnorshire; also in 
Wenlock shale of Cwm Bach, Builth; Upper Bala flags of Dry Ridge, near Horton. 
ORTHOCERAS SEMIPARTITUM (Sov.) 
Ref—Sow. Sil. Syst. t. 3. f. 9a. 
Sp. Oh.—Regularly conic, tapering at the rate of nearly two lines in one inch from a diameter of two and 
half lines ; septa slightly convex, at the above diameter slightly less than one line apart ; siphon nearly central, 
connected with the outer tube by a thick lateral plate. 
I have only seen one very ill-preserved portion of this extraordinary species, the septa of which seem to 
be figured too near each other in Mr Sowerby’s engraving above quoted. He states that the surface is smooth, 
but I have not been able to see it. 
Position and Locality.—Tilestone of Horeb Chapel, Llandovery, S. Wales. 
