OEIHOCERATID^. 
105 
Sjp. Char. Shell straight. Section elliptical, the ratio of the two 
diameters being as 12 : 8 in the type specimen, as figured by M‘Coy> 
but as 2S : 15 in the specimen in the Xational Collection. Length 
of body-chamber not ascertainable, but it was at least IJ times the 
diameter of its base. Septa very oblique, appearing somewhat 
distant in the example figured by H‘Coy, but in the adult shell 
they are distant only 1 of the diameter. Siphuucle nearly central, 
its structure being unknown. Surface of test quite smooth. 
Remarl'S. It seems to be pretty clear that the specimen in the 
National Collection is the adult form of the species. The strongly 
oblique septa and compressed form of the shell are very character- 
istic, and in these features it exactly resembles M‘Coy’s t}*pe. 
I am by no means certain that 0. pereUiptkum does not belong 
to the same group as Actinoceras imhricatum, Wahl., and A. undu- 
latam, Sow., but as there is no trace of the siphuncle in the speci- 
men before me, I cannot solve this question. 
Horizon. Carboniferous Limestone. 
LocaliUj. Cork, Ireland. 
Represented in the Collection by a single example. 
Orthoceras inaequiseptum, Phillips. 
1836. Orthoceras inrsquiseptum, Phillips, Geol. of Yorkshire, pt. ii. p. 238, 
pi. xxi. f. 7. 
1813. Orthoceras calamus, de Koninck, Precis 41^m. de G^ol., par 
J. .1. d’Omalius, p. olC. 
1844. Orthoceras calamus, de Koninck, Descrip, des Anim. Fossiles de 
la Belgique, p. 506, pi. lix. f. 2. 
1845. Orthoceratites calamus, de Verneuil, Geologie de la Riissie 
d’Europe, vol. ii. Pal»?ont. p. 356. 
1849, Orthoceratites calamus, d’Orbigny, Prodr, de Paleont. stratigra- 
phique, vol. i, p. 113. 
1851. Orthoceras calamus, Giebel, Fauna der Vorwelt, Band iii. Abth. i. 
p. 234. 
1855. Orthoceras ineequiseptum, M‘Coy, British Pal. Foss. fasc. iii. 
p. 571. 
1860. Orthoceras Martinianum, Eichwald, Lethaea Rossica, vol. i. 
Seconde Sect, de I’ancienne P^riode, p, 1218 (not of de Koninck). 
1880. Orthoceras calamus, de Koninck, Faune du Calc. Carbonifere de 
la Belgique, p. 52, pi. xxxviii. f. 6. 
Sp. Char. Shell straight, very elongated and gradually tapering. 
Length of body-chamber in the type specimen (which is imperfect) 
about five times its basal diameter. “ Septa very numerous, five 
occupying the space of one diameter in specimens varying from a 
little more than two lines in diameter (about four in a diameter when 
a little smaller), moderately concave, their edges nearly even, and 
