SILICIOUS AND HORNY SPONGES WILSON. 447 



Foreign spicules (small raphid-like oxeas, sigmas, and sigma-like 

 oxeas) occur in the alcoholic specimen at the surface in spots. They 

 are in such places abundant enough to be deceptive, making the im- 

 pression of being intrinsic elements of the skeleton. 



Holotype.— Cat. No. 21341, U.S.N.M. 



Suborder Lithistida 



Lithistida O. Schmidt, 1870, p. 21. 



The characteristic megascleres are desmas, generally united into 

 a coherent framework. 



The current internal classification of the Lithistida which we owe 

 to Sollas (1888) and which with minor changes is employed in Len- 

 denfield's synopsis (1903) is open to some criticism, 'as Dendy, 1905 

 (pp. 99, 102), and Hentschel (1912, pp. 305-06) have pointed out. 

 It remains, however, very usable, although if the subdivisions Hop- 

 lophora and Anoplia continue to be employed the Anoplia must be 

 extended to include forms with microscleres (see below. T aprobane) . 



Family THEONELLIDAE. 



Tetracladidae Sollas, 1S88, p. 284. 

 Theonellidae Lendenfeld, 1903, p. 126. 



With special ectosomal megascleres, having the character of tri- 

 enes (phyllotriaenes, discotriaenes, dicho- or trichotriaenes) . The 

 desma is tetracrepid or rarely tricrepid. With microscleres. 



Lendenfeld, 1903, changes the name (Zittel's) of the family as 

 used by Sollas; adds SulcastreUa O. Schmidt, in which the desma 

 is apparently tricrepid; and merges the following genera: Neosi- 

 phonia Sollas into Jereopsis O. Schmidt, Rimella O. Schmidt into 

 Racodiscula Zittel, ColUneUa O. Schmidt into Discodeimiia Bocage. 



The following forms not included in, or described later than, 

 Lendenfeld's synopsis (1903) fall in this family: Theonella levior 

 Lendenfeld (1906, p. 344), T. lacerata Lendenfeld (1906, p. 347), T. 

 annulata Lendenfeld (1906, p. 350), T. disci/era (1906, p. 351), T. 

 pulchri folia Dendy (19215, p. 5) ; Discodermia natalensis Kirkpat- 

 rick (19026, p. 172), D. emarginata Dendy (1905, p. 99), D. ramifera 

 Topsent (1904, p. 57), D. tuberosa Dendy (1921&, p. 6) ; Racodiscula 

 clava (Schmidt) (Topsent, 1904, p. 58). 



Genus THEONELLA Gray (1868). 



Theonella Gray, 18686. p. 438.— Sollas, 1888, p. 284.— Thiele, 1900, p. 50. — 

 Lendenfld, 1903, p. 126 ; 1906, p. 344. 



With tetracrepid desmas; with phyllotriaene ectosomal spicules., 

 clads simple or dichotomous or more complexly branched, these spic- 



