ORXnOCERATlDJL. 
67 
Sjy. Char. Section elliptical, the ratio of the two diameters in a 
specimen less compressed than is nsnally the case being as 6:8. 
The rate of increase cannot be accnratel}’ determined for the whole 
shell, but for the body-chamber it appears to be about 1 in 7. The 
body-chamber was apparently short, probably not exceeding twice 
the basal diameter, but it is not perfect enough to determine its 
length. The septa, at least those near the body-chamber, are approxi- 
mate, being about ^ the diameter distant from each other. The 
shell seems to have liad a slight constriction near the aperture. 
The siphnncle is a little eccentric, situated about | across the 
longer diameter, and obscurely beaded. 
All the specimens known are crushed casts, so that the finer 
ornamentation of the test can rarely be made out. The coarser 
consists of longitudinal, parallel ribs separated by shallow, concave 
interspaces, the whole giving a fluted appearance to the casts. 
These ridges vary in their distance apart, but there are usually 
from 30 to 35 in specimens whose broadest diameter is from 1 to 
1| inch. 
The finer ornaments (which I have only seen distinctly upon a 
specimen in the Museum of the Geological Society of London) 
consist of exceedingly fine transverse arched strise between the 
ribs, visible only with the aid of a lens. I have not observed any 
trace of smaller ridges between the large ones above described. 
Remarl s. Many examples of this species consist only of the body- 
chamber, worn down at the base in a very peculiar manner to a 
conical point. In some specimens the siphnncle remains, denuded 
of the shell, or with only traces of it crushed in the matrix. 
Horizon. Menlock Shales, Aymestry Limestone, Upper Ludlow. 
Localities. Walsall, Staffordshire ; Dudley, Worcestershire ; 
Woolhope, Herefordshire ; Presteign, Radnorshire ; Broselcy, 
Shropshire. 
Well represented in the Collection. 
Orthoceras canaliculatum, Sowerby. 
1839. Orthoceras canaliculatum, Sowerby, in Murchison’s Sil. Syst. 
p. 632, pi. xiii. f. 26. 
1854. Orthoceras canaliculatum, Salter, in Murchison’s Siluria, p. 232, 
pi. xxviii. f. 3. 
1868. Orthoceras doricum, Barrande, Syst. Sil. de la Boheme, vol. ii. 
Texte hi. 1874 (janvier), p. 242, pi. cclxix. 
? 1869. Orthoceras canaliculatum, Heidenhain, Ueber Graptolithen 
fiihrende Diluvial-Geschiebe der norddeutschen Ebene, p. 22. 
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