REVISIOX OF FRESHWATER SPONGES OF SPONGILLIDAE 71 



not yet described in detail. Consistency of live sponge recorded as 

 soft but elastic. 



Megascleres slightly ciu^ved and distinctly fusiform amphioxea, 

 armed with rather conspicuous spines except at their tips; spines 

 short and arising from a broad base; length range 250-350 n, width 

 range 8-13 m- 



Alicroscleres absent. 



Gemmoscleres sHghtly curved or almost straight amphistrongyla, 

 their central portion ranging from smooth to feebly spined, their 

 extremities displajdng an aggregation of dense spines, so that ter- 

 minally the scleres attain a clublike shape; length range 65-75 m, 

 A^idth of central stem 4 ji, of extremities 10 m- 



Gemmules abundant in mature sponge, spherical, ranging in diam- 

 eter 350-400 IS] pneumatic layer well developed and thick, consisting 

 of minute spherical air spaces; gemmoscleres embedded in this coat 

 more or less radially, often crossing each other at various angles, 

 and arranged in a singular layer; foramen distinctly tubular, porus 

 tube comparatively long, slightly exceeding level of outer gemmular 

 membrane, surrounded by a conical depression caused by slanting 

 gemmoscleres in its \dcinity. 



Distribution. — Apparentlj^ restricted to Africa, hitherto found 

 otAj in Sansibar, the Belgian Congo, and Northern Rhodesia. 



Color in life. — Has yet to be confirmed. 



Discussion. — Tliis species is most closely related to R. hemephydatia 

 in many features but can be distinguished from the latter by its 

 distinctly larger and conspicuously spined megascleres, by slight 

 though perceptible differences in the shape and length of its gem- 

 moscleres, and by the absence of mammiform aspiculous elevations 

 of the pneumatic coat in the vicinity of the gemmular micropyle. Its 

 separate specific status, at least at the present, is therefore fully 

 justified. 



The fact that the terminal aggregations of spines on the gemmo- 

 scleres of R. sansibarica are often slightly asymmetrical has caused 

 Annandale (1914) to place this species tentatively in the genus 

 Pectispongilla, an arrangement which was followed by most subse- 

 quent authors. However, the reexamination of the type during the 

 present studies proved clearly that R. sansibarica cannot possibly 

 represent a Pectispongilla species for a number of reasons. Its gem- 

 mules are moderately large to large, possess relatively long gem- 

 moscleres, and consequently a thick pneumatic coat; the spines on 

 its gemmoscleres, although occasionally irregular in length, do not 

 form unilateral arrangements of comb rows, but distinct club-shaped 

 terminal aggTegations ; microscleres of any kind are absent from 



