ART. 4 SPONGES OF CALIFORNIA de LAUBENFELS 6 



GENERAL CLASSIFICATION 



Students of sponges do not agree as to methods for classifying 

 them. One of the most recent and best of myriad systems is that of 

 Topsent (1928), which roughly is the source of the arrangement 

 herein employed. For the phylum Porifera Topsent employs 11 

 orders without diagnosing them. The following represents an at- 

 tempt to describe these orders (except one that has been dropped) 

 in a manner convenient for students who have not specialized at all 

 in the systematics of sponges, although for proper taxonomy sucli 

 descriptions are unsuitable: 



1. Calcarea: Sponges with calcareous skeletons; this may be tested 

 with acid, as calcium carbonate dissolves in most of the common 

 acids, but silica only in hydrofluoric acid. The normal inorganic 

 skeletal material in the other orders is siliceous. 



2. Hexactinellida: Sponges whose principal spicules have five or 

 six rays diverging from a central point. Such spicules may occur 

 as small or auxiliary spicules in the other orders, but not as chief 

 spicules. ; 



3. Myxospongida: Sponges with no skeleton whatever, neither 

 fiber nor spicule ; sometimes called " slime sponges." It is not known 

 whether they are primitive or degenerate, but probably they are 

 the latter. They may possibly be derived from more than one of the 

 other orders. 



4. Choristida: Sponges typically with tetraxons among their 

 principal spicules, often having a conspicuously radiate structure 

 and a cartilaginous rind, or ectosome. 



5. Hadromerina: Sponges often with pin-shaped spicules (tylo- 

 styles), asters as microscleres, corticate ectosome, and radiate struc- 

 ture. Almost any sponge lacking tetraxon spicules and having any 

 two of these features should be put in this order, 



6. Halichondrina: This order is very difficult to describe to the 

 nonspecialist. In general, there is very confused arrangement of 

 spicules, together with simplicity of spiculation. Very few mem- 

 bers of this group have any microscleres, and, if any, they are 

 few and simple. 



7. Poecilosclerina: Almost all the sponges that have any one of 

 the following characteristics belong here : (a) Larger spicules spiny ; 

 (6) chelas as microscleres; (c) fibers containing monactinal spicules. 

 If there is any possibility that the sponge for which identification 

 is sought belongs in this order, try that assumption hopefully, as 

 many more sponge species are assigned to this order than to 

 any other. 



8. Haplosclerina: Sponges with only diactinal chief spicules and 

 with only very simple microscleres, if any; they are usually markedly 



