REVISION OF FRESHWATER SPONGES OF SPONGILLIDAE 131 



Megascleres almost straight, distinctly fusiform and entirely smooth 

 amphioxea; length range 380-550 n, width range 17-21 /z. 



Microscleres very abundant in dermal membrane and symplasm; 

 true stellate forms (asters) comparatively rare, the majority being 

 slender and microspined amphioxea which bear in their central portion 

 a number of long and perpendicular rays; length range 65-75 /x, length 

 of rays 22-40 m- 



Gemmoscleres birotulates of sHghtly but distinctly unequal length, 

 with a strongly spined cyhndi'ical shaft which occasionally is shghtly 

 bent and abruptly increases in width towards the rotules; the latter 

 less distinctly umbonate as in the foregoing two species, their margins 

 incised into a number of rather sharp and recurved teeth ; length range 

 52-75 /i, thickness of shaft 3-4 /x, diameter of rotules 23-24 ju. 



Gemmules shghtly subspherical, ranging in diameter 490-600 n; 

 pneumatic layer w^ell developed and granular, consisting of minute 

 spherical air spaces; gemmoscleres with their upper rotules rarely pro- 

 jecting through its outer surface; shape of foramen could not be re- 

 solved in the material available for this study. 



Distribution. — Only known from the type locality, the Nile R. 



Color in life. — Not yet recorded. 



Discussion. — In his original description of this species, Kirkpatrick 

 (1906) hsted a number of valuable spicular differences from the pre- 

 ceding two species. Disregarding one of them, the supposedly different 

 form of the gemmosclere shafts, as incorrectly observed, the remainder 

 of criteria are in much sharper contrast to both D. plumosa and D. 

 palmeri than those separating these latter two species. The almost 

 complete absence of true asters, and their replacement by a transitional 

 amphioxous sclere with perpendicularly arranged central rays, as well 

 as the rather flattish shape of the umbonate rotules are perhaps the 

 most outstanding distinguishing criteria which clearly separate D. 

 brouni from all its congeners. However, it is to be regi-etted that no 

 data are available on the general characteristics of this species, and 

 future collections are highly desirable. 



Dosilia radiospiculata (Mills, 1888) 



Plate 11, figures 14-17 



Heteromeyenia radiospiculata Mills, 1888, p. 313. — Weltner, 1895, p. 128. — Kelli- 



cott, 1897, p. 50.— Gee, 1932c, p. 34. 

 Asteromeyenia radiospiculata Annandale, 1912a, p. 593. — Smith, 1921, p. 17. — Old, 



1936b, p. 11.— Wurtz, 1950, p. 5.— Jewell, 1952, p. 453.— Penney, 1960, p. 33. 

 Astromeyenia radiospiculata Schroder, 1927b, p. 101. 



? Heteromeyenia plumosa Weltner, 1895, p. 127. — Gee, 193 le, p. 46; 1932c, p. 25. 

 fAsteromeyenia plumosa Smith, 1921, p. 17. — Old, 1936b, p. 11.— Eshleman, 1950, 



p. 42.— Penney, 1960, p. 33. 

 fAstromeyenia plumosa Schroder, 1927b, p. 101. 

 279-430—68 11 



