148 SPONGES 



Family 4. Stellettidae, Soil Megascleres, triaenes, and rliabdi ; 

 canal system aphodal ; ground substance of choanosoine sarcenchymatous. 

 Sub-Family («). Homasterika, Soil. Never more than one form of aster. 

 Genera — Myriastra, Soil. ; Pilochrota, SolL Sub-Family (b). jEuaste- 

 RINA, Soil. With two kinds of euasters. Genera — Anthastra, Soil. ; 

 *(Teor?i<es, Crtr. [Cret. Eoc] ; t.S'^,'//e^to, O.S. [Cret. Eoc.]; iJragmastru, SoW. 

 Sub-Family (c). Sanidasterixa, Soil. With euasters and sanidasters or 

 amphiasters. Genera — Ancorina, O.S. ; Tribrachion, Welt. (Fig. 25); 

 jTethyopsis, Stew. [Cret.] ; Disijringa, Soil. (Fig. 26) ; Stry2:ihnu.^, Soil. ; 

 Seiriola, Han.; Sanidastrella, Tops. Sub -Family (d). Rhabdastkrixa, 

 Soil. With, euasters and luicrorhabdi. Genera — Ecionema, Bwk. ; 

 Papyrula, O.S. ; Psammastra, Soil. ; Penares, Gray ; Algol, SolL 



Denius y — Sterrastrosa, Soil. The characteristic microsclere a sterr- 

 aster. 



Family 5. IGeodidae, Gray. With triaenes. Sub-Family («). 

 IErylina, SolL Megascleres, orthotriaencs, and rhabdi, never ana- 

 triaenes or protriaenes ; somal microsclere a microrhalxlus or spherule. 

 Genera — fEryliis, Gray [Eoc] ; Caminus, O.S. ; Pachymutisma, Bwk. 

 Sub-Family (6). fGEODiXA, Soil. Mega-scleres rhabdi, orthotriaenes, or 

 dichotriaenes, frequently aLso protriaenes and anatriaenes. Somal micro- 

 sclere, an aster witli numerous rays. Genera — Cydomum, Flem. ; jGeodia, 

 Lam. [Cret.] ; Synops, Vosm. ; Isojjs, Soil. Family 6. fPLACOSPONGiDAE, 

 Gray. Megascleres pin-shaped monaxons (" tylostyles "), no triaenes. 

 Genera — Placospongia, Gray ; Antares, SolL ; Physcaphorn, Han. ; *Rh<i:r- 

 ella, Hinde [Jur.]. 



Genus incerti sedis — *Ophirhaphidites, Crtr. [Cret.]. 



Sub-Order 2. Lithlstida, O.S. 



Tetractinellida with a rigid skeleton, due to interlocking of special 

 (secondary) spicules, desmas. 



The classification which follows is that of Sollas, founded upon a study 

 of the living forms. In addition there are numerous fossil forms, not 

 sutKciently well characteri.«ed to be assigned a definite i)lace in this 

 system, sucli as the family Rhizomorina of Zittel, which should be divided 

 amongst the two families Corallistidae and Azoricidae ; these will be foimd 

 appended at the end of the system. The new groups and families created 

 by IlaulF, whose studies are not yet completed, are indicated in square 

 brackets in tlieir ])roper pL'uvs. 



TUIHE 1. IIoi'LOPHORA, Soil. 



With special ectosomal spicules and usually some form of microscleres. 



Demus a — ^Triaenosa, Soil. The ectosome contains megasclere.s 

 typiaiUy triaenes, sometime!?, however, monaxons (styles — ] lesmanthidar : 

 rhalxli — Sulcastrella) ; canal system aphodal. 



Family 1. fTKTRACLADiDAE, Z. Witli tetracrepid desmas and micro- 

 scleres. Genera — yTheonella, (Jray [Eoc]; f Dif^codertnia, Boc [Eoc]; 

 Racodiscula, Z. ; Kaliapsis, Bwk. ; Ncosiphonia, Soil. ; Pimella, O.S. ; 

 CoUindla, O.S. (Fig. 28, /)') ; Salrastrclln, O.S. ; *Phymatetla, Z. [Cret.] ; 

 *Aulax{n{a. Z. [Cret] ; *Callo}mjma, Z. [Cret.] ; *Trtichysycon, Z. [Cret.] ; 



I 



