14 
THE ZOOLOGICAL DEPABTMENT. 
[upper 
•which (the T. gigas), \Yhen full grown, is the largest and heaviest of 
shells, some of them weighing more than 300 pounds. The Phola- 
dacea, or Boring shells, live sunk perpendicularly in holes in rocks, or 
in sand. Tables 39-48 contain the Asiphonophora, which have the 
mantle-leaves free, and sometimes a separate single siphonal opening, 
for the emission of the water, as the Mussels and Oysters, many of 
which secrete pearls ; the brightly-coloured Spondyli, or " Thorny 
Oysters," with their rough, foliated or spiny shells, and the thin 
Placunse, or " Cake-Oysters," which are semi-transparent. In Table 
49 are shells of the Mollusca which have no distinct foot on the 
under side of the body, and which either live attached to marine 
bodies, float on the surface of the sea, or walk on their heads, as the 
Brachiopoda, which live constantly attached to marine bodies ; the 
Pteropoda, -which have an expanded fin on each side of the small foot, 
and float on the surface of the sea, especially in the evening. Of these 
the Limacina and Clio, abundant in the Arctic Seas, form a great part 
of the food of the whale. Table 50 contains the shells of Cephalo- 
pods; the animals (of which the Cuttle-fish is an example) have 
eight, ten, or many strong and elongated arms round the mouth of their 
large and distinct head, on which they crawl : the mouth is armed 
with large beak-like jaws. Their eyes are large, and their back is 
generally supported with a horny blade, sometimes strengthened with a 
shelly coat, as the cuttle bone. They have a secretion of a deep black 
colour, which they emit when in danger, and thus conceal themselves. 
They are very voracious creatures. The female of the Paper Nau- 
tilus (Argonauta) fabricates a delicate symmetrical shell, in which 
she lays her eggs, and there protects them. Both sexes of the Pearly 
Nautilus form a shell for their protection, one portion of which is di- 
vided into chambers. Some of the extinct chambered shells, as the 
Ammonite, are placed with the Nautilus Shell in Table 50. 
In some of the side Table Cases there are — a series of specimens ex- 
hibiting the structures, diseases, deformities, and reparations of shells, 
such as the distorted variety of the common Garden Snail, described as 
Helix Cornucopias ; a series of the eggs and egg-cases of Molluscs ; a 
series of specimens exhibiting the shells used for commercial purposes, 
such as the cameos, mother-of-pearl, gloves made from the byssus of 
the Pinna, the Chank shells carved by the natives of India and used 
in their temples. In another Case are specimens of the various kinds 
of Sea Slugs, or Bechedi Mar, or Trepang (Holothurm), from the 
Canton market, where they are sold as articles of food. 
THE NORTHERN ZOOLOGICAL GALLERY. 
FIRST ROOM. 
The Wall Cases contain a collection of the Nests of Birds and 
Insects, exhibiting the architecture of these animals. Among the 
more noticeable are the playing avenues of the Australian Bower 
Birds, the pendulous nests of some of the Orioles, and the gelatinous 
nests of the Esculent Swallow. The Table Cases contain specimens 
