118 
NAUTILOIDEA. 
Orthoceras digitus, de Koninck, sp. 
1880. Cyrtoceras digitus^ de Koninck, jB'aune du Calc. CarbonifSre de 
la Belgique, p. 20, pi. xxxiv. ff. 11, 12. 
Char. Shell slightly curved in the inferior portion, hut nearly 
straight above. Section circular. Bate of increase rather rapid, 
between 1 in 4 and 1 in 5. The septa are numerous and disposed 
a little obliquely ; they are not deep, and regularly concave. The 
siphuncle is situated on the ventral (?) side, near the border. The 
dimensions of the body-chamber are unknown ; probably the 
extreme tenuity of the test has caused it to be broken off before 
fossilization. The surface is almost completely smooth, except a 
few faint strise of growth, visible by the aid of a lens. The cicatrix 
is not observable, though the tip of one of the specimens in the 
Collection is preserved. 
JRemarlcs. M. de Koninck mentions the occurrence of this species 
in the Carboniferous Limestone in the neighbourhood of Bathkeale, 
Ireland, he having seen the specimen from this locality in the 
Museum of the Geological Survey at Dublin. 
Horizon. Calcaire Carbonifere = Carboniferous Limestone. 
Locality. Vise, Belgium. 
The Collection possesses two examples of this species. 
Orthoceras Frearsi, de Verneuil. 
1845. Orthoceratites Frearsi, de Verneuil, in Murchison, de Verneuil, 
and de Keyserling, Geol. de la Bussie d’Europe, vol. ii. Pal^ont. 
p. 356, pi. XXV. f. 3. 
1849. Orthoceratites Frearsi, d’Orbigny, Prodr. de Pal^ont. Strati- 
graphique, vol. i. p. 113. 
1860. Orthoceras Frearsi, Eichwald, Lethsea Bossica, vol. i. Seconde 
Sect, de I’ancienne Periode, p. 1223. 
Char. Shell straight. Section circular. Bate of increase 
about 1 in 5. Body-chamber too imperfect to characterize. Septa 
rather approximate, two lines distant in a diameter of ten lines ; 
preserving an almost uniform distance in a fragment two inches 
and two lines in length. Siphuncle small, submarginal. Test un- 
known. 
JRemarlcs. The specimen figured by de Verneuil presents the very 
anomalous character of a diminution in diameter towards the aper- 
ture, which one is inclined to think must be due to some accidental 
circumstance of preservation. This diminution, as described by 
de Verneuil, begins at the third or fourth septum nearest the body- 
chamber. One might suppose, he adds, from this that the aperture 
