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THE AMERICAN MUSEUM JOURNAL 



projections]on its surface, and for its very fragile texture. Other 

 noteworthy specimens belonging to this order are as follows : 



Spongtlla sp. (illustrated on page 231.) — This is an example of 

 the fresh-water sponges which form the only exception to the 

 rule that sponges are marine animals. In color it is usually 

 yellowish, often tinged with green or brown. It is vmiversally 

 distributed in streams and ponds. 



Pachychalina. — This genus consists of usually elongate, 

 finger-like and branching sponges in which the spicules are btiried 

 in a homy coating of spongin . The numerous excretory open ings, 

 or oscula, are conspicuously scattered over the external surface. 



FIG. 24 — THE STOLON-BEARING SPONGE (Siphonochatina stoloni/era Whitfield) 



A peculiar adaptation of the branching habit. 



Siphonochalina. — This is closely related to the preceding 

 genus, but consists of a group of tube-like individuals varying 

 in form, and with spongin of somewhat paper-like texture. 

 This genus is represented by several species, of which Siphono- 

 chalina stolonifera Whitfield is the most remarkable. This beau- 

 tifvd sponge is illustrated in the above cut of the type~specimen. 

 It consists of a number of tubes with crown-like summits, growing 



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