REVISION OF FRESHWATER SPONGES OF SPONGILLIDAE 31 



Discussion. — The general morphology of the gemmules of Eunajnus 

 crassissimus displays close affinities to that of E. fragilis, and the gem- 

 moscleres are similar in both species. However, the porus tube of the 

 former is conspicuously shorter and approaches in form that of S'. 

 ambigua and S. decipiens, and all the other criteria are in sharp con- 

 trast to E. fragilis. When fully mature the megascleres are distinct 

 amphistrongyla; the extensive amount of spongin used for the binding 

 of megascleres gives the skeleton an extremely rigid, almost stony 

 consistency; although often restricted to the base of the sponge, the 

 gemmules rarely form a distinct pavement layer. All these characters 

 are sufficient to separate this species clearly from E. fragilis. Recent 

 studies (Racek, MS.) indicate that E. crassissimus may also occur 

 in New South Wales, Australia. However, further taxonomic studies 

 are necessary before this Asian species can be reliably recorded from 

 Australia. 



Eiinapius igloviformis (Potts, 1884) 



Spo/igilla igloviformis Potts, 1884b, p. 216; 1887, p. 202.— Weltner, 1895, p. 114.— 

 Smith, 1921, p. 17.— Gee, I931e, p. 40; 1932c, p. 38; 1937, p. 285.— Old, 

 1932b, pp. 447, 469; 1932a, p. 131.— Jewell, 1939, p. 20.— Eshleman, 1950, 

 p. 38.— Wurtz, 1950, p. 4.— Penney, 1960, p. 20. 



Material. — ^Very numerous specimens and slides from the United 

 States and Canada (Gee, USNM, Jewell). 



Description. — Maturing sponge forming fiat crusts or irregular 

 growths; surface typically smooth and usually even; oscula small 

 but conspicuous, dermal membrane well developed. Skeleton con- 

 sisting of radial and transverse spicule fibers joined together by only 

 small amounts of spongin. Consistency of live sponge moderately 

 firm to fragile. 



Megascleres almost straight or only slightly curved and fusiform 

 amphioxea, entirely covered with coarse spines; length range 190-205 

 ju, width range 0-13 /x. 



Microscleres absent. 



Gemmoscleres rather stout and feebly curved amphioxea or amphi- 

 strongyla, covered with strong and irregular spines; length range 

 08-120 n, width range 4-7 n. 



Gemmules in compact hemispherical groups of 7-20, diameter of 

 inner gemmular membrane 180-200 /x; 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 tangentiaUy over the gemmules, and in an irregular 

 manner in the interstices; foramen invariably tubular, porus tube long 

 and curved, opening inward. 



