ON SOME GENERIC DISTINCTIONS IN SPONGES. 



By H. V. Wilson 



Genus TetiUa O. Schmidt 1868. Suborder Sigmatotetraxonida. 

 Tribe Sigmatophora. Family Tetillidae. 



Tetilla O. Schmidt+Chrotella Sollas, Sollas 1888. 



Tetilla O. Schm., Lcndcnfeld 1903. 



Tethya Lamarck, ;jars^ Lendenfeld 1906. 



Typically the ectosome is not a distinct layer hut shades ojf into 

 the choanosome; IJie pores ami oscula scattered, and not located in 

 special depressions. In some species, hoioever, the ectosome is to 

 some extent histologically differentiated and partially assumes the 

 cliaracter of a fibrous cortex, thus constituting an approach to Tethya. 

 And in some species there are special depressions, on the smooth 

 floor of lohich numerous small apertures (afferent pores or small 

 oscula or both?) are located; these species in respect to this feature, 

 ranging over towards Cinachyra. There is no specicd cortical skele- 

 ton. The microscleres have been lost in some species. 



Lendenfeld, 1906, merges Tetilla in Tethya (Craniella auct.) and 

 hence changes the family name to Tethydas. As I have elsewhere 

 said (George & Wilson, Sponges of Beaufort Harbor and vicinity), 

 it seems best to retain 1:»oth genera, and the family name (Totillidir) 

 may be left unclianged. 



Tetilla, the simplest and therefore presumably the ancestral genus 

 of the family, has been gradually enlarged in the practice of recent 

 writers by the incorporation in it of atypical species that depart in 

 one direction or another from the central group of typical forms to 

 which Sollas" (l('Hiiition(1888) is api)lical)I('. Thus species that 

 have diflerentiatcd in the direction of Tethya, in that tliey have a 

 fibrous cortex, are here inclu(l('(l i T.longipilis Topsnit 1904; 

 T.anomala Dendy 1905; T.horodeusis Dendy 191()). Other species 

 are classed here tlint have tlitl'erentiated toward Cinachyra in that 

 there are superiieial j)orifer()US depressions, the floor of which e.xhihits 

 pore-like a])ertures, the inhal(Mit or exhalcMit mitun^ of which !<eein.s 

 not to l)e certain (cf.Kirkpatri.-k r.MC, Deiidv TJO')), but these 

 species lack the ilbi-oiis cortex and cortical ski-h'ton of Cinachyra 



