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merous and very long or very short. The five arms may form 
simply the angles of a pentagon, or they may form the greater 
portion of the animal. Some of the larger species are exhibited 
in Wall-case 4. 
Cases 9, IO, 11 and 12.— In Case 9 begin the Echinoidea, 
or sea-urchins. The skeleton of all these consists of ten zones of 
plates closely joined and forming a sort of box. On the outer 
surface of this is an armature of spines. The form of the animal 
varies greatly, some being globular, some slightly flattened, others, 
as the “ sand-dollars,” extremely so. The spines undergo strange 
modifications. 
In the south end of Case 12 are exhibited a portion of the 
Holothuroidea , or sea-cucumbers. Several alcoholic examples of 
these will be found in the Wall-case, 3. 
In Case 12 are also found a few worms and a few species of 
the Polyzoa. Others of both groups are contained in Wall-case 3. 
Overhead in this room is suspended a life-size model of the 
enormous Octopus , or devil-fish, which occurs on the coast of 
California. 
HALL 25. 
INSECTS, CRUSTACEANS, MOLLUSKS. 
Wall-case 1 . — Collection of crustaceans. Although the 
number of species is small, those represented are valuable and 
exemplify the strange modifications of form and structure which 
are found m this group. The barnacles, as an illustration, have 
little appearance of kinship to the lobsters and crabs; but studies 
of their early stages of development prove that they are true 
crustaceans. A specimen of the giant crab from Japan is found 
on the wall of the alcove of this hall. 
Case 2. — A collection of about 2,000 butterflies and moths. 
Case 4. — With this case the visitor takes up again the mol- 
luscan series which he has been examining in the West Court (see 
page 1 1 5). Here are contained a portion of the Turbinellidce , 
continued from Case 2 7, West Court; Fasciolariidoe ; Fusidtz 
(spindle-shells), and Mitrid, (mitre-shells). 
