526 
THE VOYAGE OF H.M.S. CHALLENGER. 
tapers almost equally towards either end, and the aperture is nearly central, and situated 
in a slightly produced neck ; the entire shell is sometimes gently curved or twisted. 
Rhdbdogonium tricarinatum is common in the North Atlantic, and out of nine 
localities at which it has been taken, eight range between 390 fathoms and 1360 fathoms, 
whilst the ninth is in comparatively shallow water, near the west coast of Ireland. 
In the South Atlantic it has been observed at two Stations near Pernambuco, 350 
fathoms and 675 fathoms respectively; and in the South Pacific at eight Stations, the 
depth of which varies from 12 fathoms to 275 fathoms. It has not been noticed at any 
point in the North Pacific. D’Orbigny ’s specimens were from the Adriatic, and a few 
examples have been obtained from the Mediterranean. 
The species has been found in the Miocene of Baden near Vienna (Karrer), in the 
Subapennine Tertiary shell-sands of Italy, and in a clay of Later Tertiary age in the 
neighbourhood of Malaga (Parker and Jones). 
Rhabdogonium minutum, Reuss (PL LXV1I. figs. 4-6). 
Rhabdogonium minutum , Reuss, 1867, Sitzungsb. d. k. Ak. Wiss. Wien, vol. lv. p. 84, pi. v. 
figs. 4, 5. 
The specimens portrayed in figs. 4-6 are of stout and somewhat irregular contour ; 
the walls are thick and wanting in finish, and the margins show a tendency to become 
carinate. Such shells seldom consist of more than three or four segments. Very s imil ar 
peculiarities are exhibited by Rhabdogonium minutum, as figured by Reuss ; and although 
the term “ minutum ” scarcely applies to the recent examples, as compared with their 
congeners, they may in other respects be fitly assigned to that species. 
This form has only been observed in one locality, — off Ki Islands, south-west of New 
Guinea, 129 fathoms. 
Reuss’s fossil specimens were from the Salt-clay of "W ieliczka, in Galicia. 
Marginulina, d’Orbigny. 
Nautilus, pars, Linn6 [1767], Walker. 
Orthocera, Orthoceras, seu Orthoceratium, pars, Soldani [1791], Lamarck, Hefrance, Blainville. 
Marginulina, d'Orbigny [1826], Bronn, Roemer, Philippi, Reuss, Czjzek, Cornuel, Bailey, 
Bornemann, Costa, Neugeboren, Terquem, Parker and Jones, &c. 
Cristellaria, pars, Williamson [1858], Seguenza, Berthelin, &c. 
The descriptive characters of the genus Marginulina, as furnished by d’Orbigny in 
the “ Tableau Methodique,” are brief and insufficient ; but it is manifest from the various 
figures referred to in the enumeration of species, that it was intended to include only 
the subcylindrical as distinct from the compressed forms ol Nodosamnce ; and the fuller 
description subsequently given in the “ Vienna Basin ” Monograph, in which the globular 
shape of the segments is expressly mentioned, confirms this view. 
