REVISION OF FRESHWATER SPONGES OF SPONGILLIDAE 133 



gemmoscleres. These unusual spicules, however, cannot be con- 

 sidered a constant feature either in size, form, or abundance. Their 

 shafts are quite frequently distinctly fusiform, fully resembhng the 

 shape of megascleres, and their "rotules" represented by a small 

 number of long hooks of varying curvature. 



During the present studies it became obvious that a clear differentia- 

 tion of characters displayed by this species and H. plumosa Weltner 

 is extremely difficult, if not altogether impossible. Although the 

 former species is recorded as possessing microspined megascleres and 

 strongly recurved hooks on their longer class of gemmoscleres, this 

 condition was often also found in specimens labeled H. plumosa, 

 and many transitory spicules were present in specimens of both these 

 "species" recorded. Since H. plumosa could not be located, it is im- 

 possible to decide whether or not these two species are identical and 

 additional studies are highly desirable. 



Should later research indicate that Weltner's species is entitled to 

 specific or subspecific rank, it wiU be necessary to change its present 

 specific name, since it represents a junior homonym of D. plumosa 

 (Carter) . The nomen novum DosUia heterogena is herewith proposed. 



Genus Trochospongilla Vejdovsky, 1883 



Trochospongilla Vejdovsky, 1883b, p. 31; 1883a, p. 332; in Potts, 1887, p. 176.— 

 Weltner, 1893, p. 7; 1895, p. 120. — Girod, 1899, p. 109. — Annandale, 1911c, 

 p. 113; 1912d, p. 384; 1918a, p. 213.— Gee and Wu, 1925c, p. 11.— Gee, 

 1926a, p. 180; 1927c, p. 185; 1931e, p. 51; 1932b, p. 1; 1932c, p. 42.— Arndt, 

 1926, p. 344; 1928a, p. 78.— De Laubenfels, 1936, p. 37.— Eshleman, 1950, 

 p. 42.— JeweU, 1952, p. 452.— Simon, 1952, p. 80.— Penney, 1960, p. 55. 



Tubella Potts, 1882, p. 14; 1884, p. 216; 1886, p. 228; 1887, p. 210 (part).— 

 MacKay, 1885, p. 233; 1889, p. 87.— KelUcott, 1891, p. 104.— Weltner, 

 1895, p. 128 (part).— Girod, 1899, p. 112 (part) .—Annandale, 1908d, p. 248 

 (part); 1909f, p. 102 (part).— Smith, 1921, p. 17; 1930, p. 184.— Penney, 1931, 

 p. 240; 1960, p. 58 (part) .—JeweU, 1939, p. 20. 



Type species. — ^By original designation SpongUla erinaceus 

 Lieberkiihn (1856), declared an invalid name by Weltner (1893), 

 and replaced by that author with Trochospongilla horrida. 



Definition. — Megascleres usually short and stout amphioxea or 

 amphistrongyla, either completely smooth or covered with a varying 

 number of small to very strong spines. 



Microscleres absent. 



Gemmoscleres minute birotulates with rather stout, smooth, and 

 comparatively short shafts, and at either end with circular rotules of 

 entire margins, which frequently are recurved in the same direction; 

 in some species both rotules of equal size and shape; more often 

 outer rotule conspicuously smaller than inner; exceptionally outer 

 rotule reduced to a small disc of regular or irregular shape. 



