26 U.S. NATIONAL MUSEUM BULLETIN 2 72 



Spongilla fragilis var. minutissima Potts, 1880b, p. 357. 



Spongilla fragilis var. ininula Potts, 1880b, p. 357. 



Spongilla fragilis var. irregularis Potts, 1880, p. 357. 



Spongilla recticuba Kozhoff, 1925, p. 58. 



Spongilla fragilis var. kendelana Schroder, 1938a, p. 302. 



Spongilla fragilis var. zempoalensis Rioja, 1940b, p. 555. 



Spongilla decipiens Weber, 1890, p. 40. — Weltner, 1895, p. 114. — Annandale, 



1907c, p. 15; 1911c, p. 97; 1918a, p. 212.— Gee, 1929d, p. 297. 

 Spongilla fragilis var. decipiens Gee, 1930a, p. 74; 1931e, p. 37. 

 Spongilla ambigua Annandale, 1909e, p. 559; 1914, p. 246. — Weltner, 1913, p. 



475.— Gee, 1932c, p. 36.— Arndt, 1933c, p. 308. 



Material. — Extremely numerous specimens and slide material; 

 EUROPE: Germany, Austria, Czechoslovakia, Hungary, Switzer- 

 land, Netherlands, Poland, U.S.S.R.; NORTH AMERICA: U.S.A., 

 Alaska, Canada; ASIA: Malaysia, Indonesia, China, Japan; AFRICA: 

 Congo, Rhodesia, Natal; AUSTRALIA: New South Wales. 



Description. — Mature sponge invariably forming flat crusts of 

 varying dimensions; surface typically smooth and usually even; 

 oscula small but conspicuous, often producing radial canals in lotic 

 environment; dermal membrane well developed. Skeleton consisting 

 of radial and transverse spicule fibers, joined together by only small 

 amounts of spongin. Consistency of live sponge extremely fragile 

 and soft. 



Megascleres almost straight or only slightly curved, fusiform 

 amphioxea, invariably entirely smooth; length range 180-270 /i, 

 width range 5-12 /x. 



Microscleres absent. 



Gemmoscleres slender to rather stout and inconspicuously curved 

 or almost straight amphioxea or amphistrongyla, typically covered 

 with a varying number of conspicuous spines that often are aggre- 

 gated at the tips of the scleres; length range 75-140 fj., width range 



2-7 /x. 



Gemmules moderately abundant in mature sponge ; either forming a 

 distinct pavement layer, fastened to the substratum, when sponge is a 

 flat crust; or also present in groups of 2-5 scattered throughout the 

 body of the sponge, when this displays a more massive mode of growth; 

 diameter of inner gemmular membrane 180-290 n; pneumatic layer 

 extremely well developed, consisting of large polygonal air spaces, 

 and forming a continuous coat over all gemmules; gemmoscleres 

 embedded in this layer strictly tangentially over the gemmular 

 membrane, and in an irregular manner in the interstices; often 

 arranged in two separate tiers above the gemmules, separated from 

 each other by the thick pneumatic coat; foramen invariably tubular, 

 porus tube of varying length and curvature at least reaching to surface 

 of pneumatic layer, opening outward. 



Distribution. — This species has a truly cosmopolitan distribution, 



