18 U.S. NATIONAL MUSEUM BULLETIN 272 



Carter (1881a), by considering the clearly distinct species S. cere- 

 bellata Bowerbank a "variety" of iS*. alba, has thus founded a taxonomic 

 confusion of these two species which has spread unchallenged to the 

 present day. The aS'. cerebellata group of species apparently has been 

 confused with *S. alba merely by the superficially similar arrangement 

 of recurved spines on the tips of gemmoscleres in both species and will 

 be dealt with in this paper under a new generic name. 



Material collected for a separate study (Racek, MS.) on Australian 

 spongillids revealed the presence of S. alba in brackish waters of 

 Queensland. Since part of this material is also present in the collection 

 of this study, S. alba is herewith recorded for the first time as occurring 

 in Australia. Material collected for and deposited in the Riksmuseum 

 at Stockholm, also examined during the present studies, has estab- 

 lished the first record of occurrence for this species in the Amazon R., 

 South America (RMS no. 94). 



Spongilla cenota, new species 



Plate 1, figures 8-10, 16 

 Spongilla lacustris Old, 1936a, p. 29. — Rioja, 1940a, pp. 174, 186. 



Material. — Several fragments of dry sponge, collected by M. 

 Goodnight and L. J. Stannard, June 1951 in Cenote Xtoloc, near 

 Chichen Itza, Yucatan, Mexico — Holotype, no. 90328 (Penney); 

 paratypes, several smaller fragments from the same locality, no. 90329 

 (Penney). 



Description.— Sponge apparently forming irregular, and more or 

 less massive cushions of moderate size; surface, not discernible in the 

 dry holotype, described by Old (1936a) as smooth; oscula apparently 

 small and inconspicuous. Skeleton consisting of a dense network of 

 slender primary and secondary fibers, held together by only little 

 spongin, as in jS'. alba. Consistency of live sponge not yet observed, 

 that of the dry holotype firm but rather brittle. 



Megascleres comparatively stout and almost cylindrical amphioxea 

 with more or less abruptly pointed tips, completely smooth; length 

 range 310-410 n, width range 14-22 ju. 



Microscleres very numerous in both dermal membrane and syin- 

 plasm; they are very similar to those of S. alba, i.e., very slender and 

 only very slightly curved amphioxea, covered with small granules or 

 spines at their tips and with a group of long and erect spines in their 

 central portion where they often form terminal knoblike inflations, 

 length range 68-123 n, width range 2-3 n. 



