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modificatioris of this pattern. The arms may be more numerous 
and very long and 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, 10, 11 and 12. — In case 9 begin the Echinoidea, or 
Sea-urchins. The skeleton of all these consist of ten zones of 
plates closely joined and forming a sort of box. On the outer sur- 
face 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 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 AND MOLLUSKS. 
Case 1. — Collection of Crustaceans. In the south end are a 
few Cephalopods. The glass models show several stages in the 
development of the Lobster. 
Case 2.— -A collection of about 2,000 Butterfllies and Moths. 
This hall also contains shell cases 21 to 32, for an account of 
these see south court, page 91. 
Study Collection. 
The study collections of mammals. Fishes and Reptiles, con- 
sisting of thousands of specimens contained in tin air tight cases 
and glass jars, is located in the balcony over the south entrance, 
and is accessible during museum hours to those who may desire 
to study the material or compare specimens. Every attention is 
paid to this important adjunct to zoological material for the assist- 
ance of scientific investigation and it is hoped that they may 
eventually be ranked among the most important collections in the 
United States, 
