16 
ZOOLOGICAL COLLECTIONS. 
[UPPER 
In Tables 19, 20 are the Strombs and Carrier-shells, which have a 
compressed foot for leaping. The Carrier-shell has the peculiarity 
of attaching to the outer surface, as it increases in size, stones, frag- 
ments of other shells, coral and other marine substances, and has 
been called "the Conchologist " and "the Mineralogist," according as 
shells or minerals preponderated. 
Tables 21-25. The Scutibranchous Mollusca, the gills of which con- 
sist of lamellae, forming one or two series on the back of the neck or 
on the under edge of the mantle round the foot ; such as the Trochidae, 
the Haliotidae or Earshells with their pearly lustre ; the Fissurellse or 
Keyhole limpets ; the Limpets with their simple conical shells, and the 
many-valved Chitons, which have a series of eight shelly pieces or 
" valves " down the back of the animal. 
Tables 25-30. The Heterobranchous Gastropods, with variously- 
formed respiratory organs. The Bullidse are placed here, with their 
curious strong gizzards ; the Bubble shells, the Aplysia or Sea Hare, 
which feeds on sea-weeds and discharges a deep purple fluid when 
danger approaches ; the Helicidse, or Snails and other allied families, 
which live on land and have cylindrical retractile tentacles. 
Tables 31-48. The Bivalve shells or Conchifera; the animal 
of these is enclosed between two shelly valves, united by a liga- 
ment. Tables 31-38 contain the Siphonophora, which have the 
mantle closed behind, and furnished with two apertures, the lower for 
the admission, and the upper for the emission, of the water from the 
mantle cavity. Some of these, as the Veneridse and other families, 
crawl on a compressed foot, while the Cockles have an elongated foot, 
angularly bent in the middle, and fitted for leaping. Near these, but 
with a small rudimentary byssiferous foot, are the Tridacnse, one of 
which (the T. gigas), when 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 
Placunae, or " Cake-Oysters," which are semi-transparent. 
In Table 49-50 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 (Brachiopoda), or float on the surface of the sea (Ptero- 
poda), or walk on their heads (Cephalopoda). The Pteropoda have an 
expanded fin on each side of the small foot. Of these the Limacina and 
Clio are so abundant in the Arctic Seas as to form a great part of the 
food of the whale. The animals of Cephalopods (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, some- 
times strengthened with a shelly coat, as the cuttle bone. They have 
