GALLERY.] NATURAL HISTORY. 25 
shells of the Brachiopodous Mollusca, which live constantly attached 
to marine bodies by a ligament passing through a notch in one of the 
valves or by the surface of the valve itself. They are furnished with 
two spiral arms, one on each side of the mouth, enclosed between two 
leaves of a mantle, protected by two symmetrical shelly valves, as 
Terebratulidce , Lingulidce , Discinidce, and Craniadce. 
The shells of Pteropodous Mollusca. The animals are furnished 
with an expanded fin on each side of the very small, sometimes scarcely 
visible foot, on the under side of the more or less developed head. 
They float on the surface of the sea, especially in the evening, as the 
families Cavolinidce , Cymbuliadce , and Limacinidce. 
Table 50. The shells of Cephalopods ( Cephalopoda). These 
animals are furnished with eight, ten, or many strong elongated arms 
round the mouth of their large and distinct head, on which they crawl 
with their head downward, and catch objects which they bring within 
reach of their mouth, which is armed with large jaws. They have 
large eyes, and the back is generally strengthened with a calcareous 
blade, sometimes strengthened with a shelly coat as the cuttle-bone, 
or with a chambered shell like the Nautilus . 
The Cuttle-fish ( Antipedia ) are naked, often furnished with an in¬ 
ternal dorsal blade; the head separate, with eight or ten arms and 
only two gills, as the Sea Spiders with only eight arms; they have no 
shells. The Cuttle or Sleave fish with ten arms, two being longer 
than the rest. Some of these have only an internal dorsal blade, as 
the Sea Sleave (Loligo), with a horny blade; the Cuttle-fish (Sepia), 
with a calcareous spongy dorsal shell: others have a chambered shell, 
which is partly visible in the front and back of the hinder portion of 
the body, as the Spirula or Post-hern shell: these differ from the 
Nautili in the small size of the terminal chambers. 
The Nautilus is the only recent representative of the other groups, 
which are abundant in the fossil state. The animal is without fins, en¬ 
closed in the last chambers of a many-ehambered external shell, with 
an indistinct head furnished with very numerous cylindrical annulated 
arms. They have four gills. 
JOHN EDWARD GRAY. 
March 4, 1856. 
