154 SPONGES 



substance round the chambers clear ; canal system eurj'pylous. Genera — 

 iSpoJi5f<'/m, Ndo.; Vclinea,\os,m..; Psammoclema, Marsliall; Psammopemma, 

 Marshall. Family 3. Aplysixidae, F.E.S. Fibres hollow, canal system 

 aphodal. Genera — Aphisina, Ndo. (Fig. 40); Luffaria (Duch. et Mich.), 

 O.S. ; Veronfjia, Bwk. ; Thorecta, Ldf. 



Ordeu 2. Dendroceratina ( = Hexaceratina, Ldf., pars). 



Spongin fibres dendritic, arising from a basal plate of spongin, and 

 not anastomosing. 



Family 4. Aplvsillidae, Vosm. Canal system euryjiylous, with 

 large elongated chambere ; in DarwincUa, spicules of spongin. Genera — 

 Aplijsilla, F.E.S. ; DaricineUa, Miiller ; lanthclla, Gray ; Dendrilla, Ldf. 

 (Here Hexadella, Tops., finds its nearest allies, and perhaps also 

 Halisarca, Duj.). 



Keratosa (? Foraminifera) incerti sedis (Haeckel, 1889 [8]). 



Family — Ammoconidae. " Keratosa without sjwngin fibres. Pseudo- 

 skeleton composed of xenophya (or manifold foreign bodies), which are 

 disposed in the thin malthar plate of the porous tubular body. Canal 

 system tubular, developed on the Asconal type (similar to that of the 

 Asconidae)." Genera — Ammohinthus, H. ; Ammosolenia, H. ; Ammo- 

 conia, H. ; Prophysema, H. Family — Psamminidae, Ldf " Keratosa 

 without spongin fibres. Pseudo-skeleton composed of xenophya . . . 

 whicli are cemented together and enclosed by the transparent maltha. 

 Canal system vesicular, developed on the Leuconal type (similar to that 

 of the Spongeliidae)." Genera — Psamminn, H. ; Holopsamma, Crtr. ; 

 Psaiiunopemma, Mai-shall. Family — Staxnomidae, H. " Keratosa with 

 a fibrillar spongin skeleton, composed of thin, siuii)le, or branched spongin 

 fibrillae, never anastomosing or reticulated. Pseudo-skeleton composed 

 of xenophya . . . which are crowded in the transparent maltlia, never 

 in the homogeneous fibrillae. Canal system vesicular ... on the 

 Leuconal type. . . ." Genera — StannophijUuiii, H. ; Stannariuyn, H. ; 

 Stannoma, H. 



Grade IV. Myxospongida, Soil. 



Sponges devoid of a skeleton in any form. 



Family 1. Oscarellidae, Ldf. With spherical ciliated chambers. 

 Genus — OscareWd, Vosm. (Fig. 41). Family 2. Hali.sarcidae, O.S. "With 

 elongatwl, sack-like ciliated chambei-s. Genera — Halifurai, Duj.; Bajuhts, 

 Ldf. ; Hexadella, Tops. 



Appendix to Classification. 



Under the names Octactinellida and HeteracHnellida, Hiude (1887) 

 has described two groups of Palaeozoic sponges, each witli a veiy aberrant 

 type of spicule, which cannot be brought either under the triaxon or 

 tetraxon type. 



In the Octactinellida, rejiresented by the single genus Astraeospongia 



