REVISION OF FRESHWATER SPONGES OF SPONGILLIDAE 29 



Eunapius michaelseni (Annandale, 1914) 



Plate 2, figures 5, 6 



Spongilla michaelseni Annandale, 1914, p. 239. — Gee, 1931e, p. 43; 1932c, p. 40. — 

 Topsent, 1932b, p. 1002.— Arndt, 1933c. p. 308; 1936, p. 15.— Penney, 1960, 

 p. 24. 



Material. — Three slides from the type (HM no. 1854), Zambesi 

 R., Africa. 



Description. — Sponge, according to Annandale (1914), forming 

 thin flat crusts of moderate dimensions; oscula small and inconspic- 

 uous, dermal membrane moderately developed, subdermal space 

 relatively small. Skeleton consisting of noncoherent radial spicule 

 fibers, joined together by an irregular network of spicules and only 

 small amounts of spongin. Consistency of live sponge moderately hard 

 but brittle. 



Megascleres feebly curved, fusiform smooth amphioxea; length 

 range 290-360 n, width range 10-18 /x- 



Microscleres absent; a number of immature gemmosclercs occasion- 

 ally present in the slides examined. 



Gemmoscleres moderately stout, straight or feebly curved amphi- 

 strongyla, covered mth characteristic spines aggregated near the 

 tips of the scleres, where they are conspicuously recurved; sometimes 

 an apical spine present on one or both tips; length range 75-145 n, 

 width range 5-15 /z. 



Gemmules subspherical, somewhat depressed, and small; diameter 

 of inner gemmular membrane 220-340 /z; not forming distinct pave- 

 ment layer, but loosely occurring together in small groups near the 

 base of the sponge; pneumatic layer moderately thick, consisting of 

 large polygonal air spaces, not forming a continuous coat over the 

 gemmules; gemmoscleres embedded in this layer more or less tangen- 

 tially; foramen distinctly tubular, porus tube rather stout and straight. 



Distribution. — Hitherto only known from central Africa. 



Color in life. — Light gray. 



Discussion. — Unless more material of this species will become 

 available, its correct relationship to other species of this genus will 

 be diflBcult to assess. E. michaelseni differs from E. fragilis by the 

 presence of free gemmules, as well as by quite characteristic gemmo- 

 scleres; an additional criterion, the presence of free microscleres, as 

 described by Annandale (1914) and quoted by Arndt (1933c), must 

 be dismissed since these scleres represent immature gemmoscleres. 

 The species discussed also differs from E. nitens, another African 



