THE PORIFERA OF THE SIBOGA-EXPEDITION 



il 

 the genus spirastrella 



BY 



G. C. J. VOSMAER 



With fourteen plates 



I. DEFINITION OF THE GENUS SPIRASTRELLA. 



The genus Spirastrella was established by Oscar Schmidt ([868 p. 17) for a "nova 

 species" (S. cunctatrix), characterised by possessing "in der Rindenschicht eine eigenthümliche 

 Art von strahligen Kieselkörperchen, deren Strahlen spiralig gestellt sind". These spicules 

 are now called spinispirae 1 ). Ridley (1884 p. 467) accepted the new genus and correctly said 

 that it must receive all "those free compact Suberitidae, with skeleton spinulate, whose flesh- 

 spicule is a modified stellate . . . ." 2 ) Ridley & Dendy gave (1886 p. 490) a short diagnosis 

 of the genus, vvhich they fundamentally retainecl in the Monaxonida of the Challenger (1887 

 p. 229): "Sponge usually massive. Megasclera all monactinal, stylote or tylostylote. Microsclera 

 spined spirulae, occurring mainly as a dermal crust". The authors state, that the genus contains 

 many species, to which "the Challenger adds three new ones". In 1888 (p. 57) and 1890 (p. 398) 

 Lendenfeld slightly modified the diagnosis. Keller (1891 a p. 322 — 323) defines Spirastrella 

 as follows : " Krustige oder massige Spongien mit wenig cavernösem Gewebe, welche in ausseren 

 Habitus an Suberites erinnern. Spongïn sparlich oder fehlend. Megasklere sind tylostyl. Mikrosklere 



i) VOSMAER I902 p. 108. 



2) It is cleav what Ridley meant; I have shown, however, that the spicule under consideration is not a modified aster 

 (1909 a. p. 642 — 648). 



SIKOGA-EXPEDITIE VI«'. ■ 



