CEPHALOPODA. 185 
not exist in very deep water. They were probably limited to 
a depth of 20 or 30 fathoms at the utmost.* 
It is certain that the sexes were distinct in the fetrabranchiata. 
M. D’Orbigny, noticing that there were two varieties of almost 
eyery kind of ammonite—one compressed, the other inflated 
—naturally assumed that the first were the shells of male indi- 
viduals (3), the second of females (9). Dr. Melville has made 
a similar suggestion with respect to the nautili; namely, that 
the umbilicated specimens are the males, the imperforated shells, 
females. Professor Van der Hoeven has described the difference 
in the shells of the two sexes; ¢ but these are trivial as com- 
pared with those presented by the animals. The most marked 
is that while the female has twelve retractile tentacles, the male 
has only eight, while the other four tentacles are coalesced 
together to form an organ called the spadia. 
In 1865, M. Barrande published the plates to his second 
volume on the Cephalopods of Bohemia. We have not been 
able to see this work : butit contains 107 plates, with figures of 
200 species of cephalopods, belonging to the genera Coniatites, 
Nothoceras, Trochoceras, Hercoceras, Litwites, Phragmoceras, Gom- 
phoceras, and Ascoceras. 
FAminty I.—NAUTILIDA. 
Shell. Body-chamber capacious. Aperture simple. Sutures 
simple. Siphuncle central or internal. (Figs. 50, 51.) 
NAUTILUS, Breynius, 1732. 
Shell involute or discoidal, few-whorled. Siphuncle central or 
sub-central. 
In the recent nautili, the shell is smooth, but in many fossil 
species it is corrugated, like the patent iron-roofing, so remark- 
able for its strength and lightness, (Buckland.) See Pl. II., 
Fig. 10. 
The wmbilicus is small or obsolete in the typical nautili, and 
the whorls enlarge rapidly. In the palsozoic species, the 
whorls increase slowly, and are sometimes scarcely in contact. 
The last air-cell is frequently shallower in proportion than the 
rest. 
* By deep water, naturalists and dredgers seldom mean more than 25 fathoms, a 
comparatively small depth, only found near coasts and islands. At 100 fathoms the 
pressure exceeds 265lbs. to the square inch. Empty bottles, securely corked, and sunk 
with weights beyond 100 fathoms, are always crushed. If filled with liquid, the cork 
is driven in, and the liquid replaced by salt water; and in drawing the bottle up again 
the cork is returned to the neck of the bottle, generally in a reversed position, (Sir F; 
Beaufort.) 
¢ Annals of Natural History, vol. xix. 1857. 
