SILICIOUS AND HORNY SPONGES WILSON. 473 



stocks of the Haiichondrina (Chalininae and various Desmaci- 

 donidae). Dendy (1905) made an important advance by clearing 

 away these types, the similarity of which to the Keratosa he 

 looks on as the result of convergent evolution, designating them as 

 pseudoceratose forms. A monophyletic group (Euceratosa) is thus 

 left, the basal family of which in Dendy's scheme is the Darwinel- 

 lidae. 



The genera included by Lendenfeld in the Monoceratina but 

 which, from the point of view just stated, should be excluded as 

 pseudoceratose sponges, are Aulena (assignable as Lendenfeld re- 

 marks. 1889, p. 90, to the Desmacidonidae — the other Aulenidae are 

 probably distributable among the remaining Keratose families), 

 Chalinopsilla (assignable to the Chalininae, see Lendenfeld, p. 121), 

 Phoiiospongia and Signiatelld (assignable to the Desmacidonidae — 

 see George and Wilson, 1919, p. 153, where the subfamily Phori- 

 osponginae is retained in an emended sense). Lendenfeld ? s sub- 

 families under the Spongidae continue to be useful in practical work 



Family DARWINELLIDAE 



Darwinellidae Mekejkowsky, 1S7S, p. 44. — Yosmaer, 1SS7, p. 366. — Top- 

 sent, 1905, p. clxxiii. — George and Wilson, 1919, p. 163. 



Darwinellidae plus Apli/sillidae Lendenfeld, 1889, p. 672. 



Apliixillidae Dendy, 1905, p. 203; 1916&, p. 95.— Row, 1911, p. 359.— Hent- 

 schel, 1912, p. 429. 



Keratosa with eurypylous and large flagellated chambers; with 

 a skeleton composed of separate horny fibers that ascend from the 

 base of the sponge and are simple or branched, or the skeleton may 

 be reticulate; "spicules'' of spongin may also occur; the spongin 

 ribers contain a medulla or pith and lack foreign mineral particles. 



Genus IANTHELLA Gray (1869). 



Ianthella Gray, 1S69, p. 49.— Polejaeff, 1SS4, p. 22.— Lendenfeld, 18S9, 

 p. 683. 



Large, lamellar or cup-shaped sponges, pedunculate below ; lamella 

 or wall thin as compared with area of sponge surface ; surface conu- 

 lose. Skeleton a coarse and regular reticulum, made up of large main 

 fibers which radiate from the peduncle to the margin of the lamella, 

 and connectives extending at right angles to the former. Main 

 fibers fascicular and, sometimes, at any rate, bandlike, the bands set 

 edgewise to the surfaces of the sponge; connectives simple, slightly 

 fascicular, or resembling the main fibers in being very fascicular and 

 bandlike. From the reticulum small simple fibers, originating at or 

 between the nodes of the reticulum, pass vertically to both surfaces 



