16 



BRANCH PORIFERA 



no commercial value. Example, Grantia. (2) The silicious 

 sponges, in which the skeleton is largely silica. Example, 

 Euplectel'lfi. (3) The horny sponges of commerce. Euspongia 

 group. To this group belong the half-dozen species of Florida 

 and the Mediterranean and the Red Seas. Our American sup- 

 ply conies principally from Florida and the Mediterranean Sea 



Fig. '.). — ,\ sponm' auction at Aiu-lutc. (Hepurt U. S. F. C, 1002' 



from water not exceeding 30 fathoms dccii. Examples of this 

 group are Sjianyia, and the fresh-water forms of the genus 

 Spongilla. 



Most zoologists make but one class of porifera; others, two 

 classes: 



I. Calca'rea. 



II. Noii-calca'rea. 



