56 NATURAL HISTORY. [n. ZOOL. GAL. 
Gray, from the Cape of Good Hope. The Tetrapturi 
differ from the Common Sword Fish ( Xipkias ) by having 
ventral fins, and two small crests, parallel to one another, 
on each side of the tail; whilst the Xiphiae have no ventral 
fin, and only one caudal crest. 
Over the door is a specimen of the Pirarucu (Sndis 
gigas , Cuv.), from the rivers of British Guiana. 
TWELFTH AND THIRTEENTH ROOMS. 
The first of these Apartments, till lately, held the Col¬ 
lections of British Birds and British Shells, with a small 
assemblage of Birds 5 Eggs. These have been removed, 
and with the general collection of Birds and Shells, which 
filled the Thirteenth Boom, are now in progress of re¬ 
arrangement in the Eastern Zoological Gallery. 
The Thirteenth Boom being closed for repairs, Visitors, 
previous to arriving at the remainder of the Zoological 
Collection, are obliged, for the present, to return to the 
Hall and pass through the Gallery of Antiquities. 
NOBTHEBN ZOOLOGICAL GALLEBY. 
ROOM I. 
The Table Cases contain the Sponges and Coral¬ 
lines, which have but a very doubtful claim to be re¬ 
garded as belonging to the animal kingdom. 
The Sponges, Tables 1—6, resemble the Corals in 
various particulars, but their animal nature is not distinctly 
made out; those found in collections are merely the skele¬ 
tons of the living mass, entirely destitute of the gelatinous 
portion which constitutes the animal, if it be really of that 
nature. Some naturalists have considered these skeletons, 
or Sponges, as analogous to the stems of Antipathes , or 
Black Coral, and consequently to the axes of zoophytes; 
and have fancied that, when alive, they were covered, like 
the Antipathes , with a perishable crust, consisting of the 
dried polypes. But recent observations on them in their 
living state have not verified this theory; for they have 
been found to be entirely destitute of any polypi, to be 
mere living masses, covered with a gelatinous coat, and 
absorbing water through the small pores spread over their 
surface, and emitting it hy the larger scattered holes 
called oscula; and though the fibres of many of the 
