ACTIN-OCEEATID^. 
179 
1857. Orthoceras cochleatum, Boll, Beitrag zur Kenntniss der Silur. 
Ceph., in Arcliiv fur die Natiu'kimde von Mecklenburg, p. 21, 
Taf. V. f. 17. 
1860. Actinoceras cocJileatum, Eicbwald, Letbsea Bossica, Seconde 
Section de I’ancienne Periode, vol. i. p. 1253. 
1861. Orthoceras crassiventre, Schmidt, Archiv fiir die Naturkunde 
Liv-, Ehst- und Kurlands, p. 194. 
1866. Orthoceras cochleatum, Barrande, Syst. SiL de la Bolieme, vol. ii. 
Texte iii. 1874, p. 695, pi. ccxxxiii. ff. 12, 18, pi. ccxxxvii. ff. 8-10, 
pi. ccccxxxix. 
1876. Orthoceras cochleatum, Eerd. Koemer, Lethsca geognostica, 
Taf. xvi. f. 5. 
1880. Orthoceras cochleatum, Kjerulf and Gurlt, Die Geologie des slid- 
lichen und mittleren Norwegen, p. 68. 
1880. Orthoceras cochleatum, Angelin and Lindstrom, Eragmenta Silu- 
rica, p. 6, tab. viii. ff 1-3, tab. x, f. 6. 
1885. Orthoceras cochleatum, Lindstrom, List of the Fossils of the 
Upper Silurian Formation of Gotland, p. 6. 
[Not 1882. OHhoceras {Actinoceras) cochleatum, Blake, British Eoss. 
Ceph. pt. i. p. 161, pi. xv. ff. 7, 8.] 
Sp. Char. Shell large. Section circular ? Bate of increase about 
1 in 6. Septa distant about the diameter of the shell. Siphuncle 
submarginal, very large, rather less than ^ the diameter of the entire 
shell, as nearly as can be estimated from imperfect specimens. The 
form of each siphuncular segment is that of a very compressed 
spheroid whose height is a little more than ^ that of its breadth. 
The test has not been observed, but in a large individual figured by 
Barrande {loc. cit. pi. ccccxxxix. f. 1) the impression of its orna- 
ments (?) were seen. The markings consisted of longitudinal and 
transverse striae, about equally spaced, so as to form a network of 
nearly square meshes. 
Remarlcs. This fine species is always found in a fragmentary con- 
dition owing to the fragile nature of the septa. The siphuncle is 
often found detached, as are those of Actinoceras and Huronia from 
the Niagara Group of Drummond Island, Lake Huron. It is usually 
filled with coarsely crystalline calc- spar, and polished sections gener- 
ally show more or less distinct traces of the endosiphon. 
Barrande (loc. cit. p. 696) describes the siphuncle as having an 
elliptical form ; but this must be the result of pressure, because I 
have a specimen before me in which it is perfectly cylindrical, and 
so most probably was the shell. 
Horizon. Upper Ludlow. 
Localities. Wisby, Island of Gothland, Sweden ; Island of Biigen, 
Germany. 
Well represented in the Collection. 
N 2 
