REVISION OF FRESHWATER SPONGES OF SPONGILLIDAE 67 



Material. — Numerous slides of specimens from various localities 

 in the United States (Jewell, N. Gist Gee), India (IM) and Indonesia 

 (AusM); slide of type of S. c. var. insularis (IM). 



Description. — Sponge, according to previous descriptions, form- 

 ing thin and small cushions of a rather even surface; oscula numerous 

 but inconspicuous, dermal membrane well developed. Skeleton con- 

 sisting of irregular spicule fibers, joined together by a smaU amount 

 of spongin. Consistency of live sponge soft. 



Megascleres slender, fusiform and sharply pointed amphioxea, 

 sparsely microspined except at their tips; length range 240-300 n, 

 width range 9-11 m- 



Microscleres absent. 



Gemmoscleres typically slender amphistrongyla, their slightly 

 curved shafts armed with a variable number of small conical spines, 

 and terminally with one to several rows of radiating slightly recurved 

 spines, arranged in such a way that pseudorotules are produced; 

 length range 60-75 n, width range 3-5 fi. 



Gemmiiles moderately abundant to abundant in mature sponge, 

 spherical, ranging in diameter 370-450 n; pneumatic layer well de- 

 veloped and thick, consisting of minute irregular air spaces; gem- 

 moscleres embedded in this coat more or less radially, but often 

 crossing each other at various angles, arranged in one layer only, 

 their distal pseudorotules not penetrating the outer getnmular mem- 

 brane; foramen distinctly tubular, porus tube short and straight, in 

 length not reaching to level of outer gemmular membrane; gem- 

 moscleres in the vicinity of this tube displaced and slanting, forming 

 a crater-like depression around the micropyle. 



Distribution. — Discontinuous, recorded from various localities in 

 the United States, ranging to Mexico; also recorded from China, 

 Japan, and parts of southeast Asia; record from Australia (Gee, 1935) 

 a result of wrong identification. 



Color in life. — Ranging from flesh colored to light green. 



Discussion. — The great variability of the gemmoscleres in this 

 species makes it difficult to decide how many different species of this 

 and other genera have been described under the name of Meyenia 

 crateriformis Potts. Similar difficulties were encountered by a number 

 of authors who were unable to interpret the greatly inconsist- 

 ent shape of the pseudorotules and repeatedly shifted the species 

 discussed from one subfamily to the other. Since pseudoro tides are 

 often produced in a number of other Radiospongilla species, this 

 criterion alone cannot possibly be used for their reliable specific 

 separation. Gee's (1935) identification of a sponge from Australia 

 under the name of Ephydatia crateriformis (reexamined as a slightly 

 atypical specimen of R. sceptroides) and Arndt's (1930a) comparison 



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