SILICIOUS AND HORNY SPONGES WILSON. 319 



Protriaenes and pro-mesotriaenes are listed by Lendenfeld, not by 

 Sollas and Thiele ; probably rubbed off in the latter specimens. The 

 anatriaenes vary in details of shape (cf. figs, of Thiele and Lenden- 

 feld) ; an outward curvature of the clads is pronounced in Lenden- 

 feld's specimen. Minute dermal anatriaenes, some reduced, are 

 inconstant in the species ; present in Lendenfeld's specimen (Lenden- 

 feld, 1910, p. 73). 



There is some inconstancy (variation) in the type with respect 

 to the microscleres. Thus the oxyspherasters listed by Sollas and 

 Lendenfeld are not recorded by Thiele. The choanosomal oxyaster 

 varies a good deal in size; total diameter in Sollas's type 21-36 p. 

 (Lendenfeld, 1910, p. 77) ; somewhat smaller in Thiele's specimens; 

 in Lendenfeld's specimen along with reduction of rays to 3-4 the 

 total diameter rises to 4G y,. The minute strongylaster has a tendency 

 to be irregular (Thiele, Lendenfeld). 



The variety which I make is especially characterized by the pres- 

 ence of the cortical spherasters, which are not recorded for the type. 

 The choanosomal oxyasters are larger than in the type. In the 

 minute strongyl asters the rays are fewer than in the type and rela- 

 tively longer, the centrum correspondingly smaller. 



Genus SIDONOPS Sollas (1889). 



Sidonops Sollas, 1889, p. 277. — Lendenfeld, 1903, p. 99. 



Synops Vosmaeb plus Geodia Lamarck part, Sollas, 1888, pp. 227, 244. 



In skeleton, habitus, and arrangement of orifices, not differing 

 from Geodia. With incurrent cribriporal chones not different from 

 those of Geodia. With excurrent uniporal chones, or with ordinary 

 efferent canals that open by simple oscula. 



For the group of forms with incurrent cribriporal and excurrent 

 uniporal chones, Sollas in 1888 (p. 227) used Synops Vosmaer. But 

 the pores of Synops are simple instead of cribriporal. Sollas there- 

 fore (1889) renamed his group of forms, Sidonops. Sy?wps Vosmaer 

 is regarded as synonymous with, and is merged in, the earlier Isops 

 Sollas. 



Lendenfeld, 1903, includes under Sidonops a number of species, 

 listed by Sollas and other authors under Geodia, in which the 

 species records leave it uncertain whether excurrent chone-canals 

 are present. The oscula in these species (Geodia flemingii, tubercu- 

 losa, reticulata, aerolata, media) are said to be simple, scattered, or 

 grouped. It is possible that some of them are the apertures of 

 excurrent chones, or on the other hand only the openings of efferent 

 canals of the ordinary tetraxonid type. I have explicitly indicated, 

 in the genus definition, the existence of this group of species. If 

 excurrent chones are really absent in this group, it might well 



