SPONGES 151 



radiate in the body, forms longitudinal fibres in the stalk. Genera 

 Stylocordyla, W. Th. (Fig. 38) ; Cometella, O.S. ; Halicometes, Tops. 



SUB-ORDER 2. I-CLAVULINA, Vosm. 



Megascleres monactinal, usually pin-shaped tylostyles, rarely styles. 



FAMILY 1. JCLIONIDAE, Gray. Boring Clavulina. Genera jCliona, 

 Grant [Cret. Eoc. Mioc.] ; Dotona, Crtr. ; jThoosa, Hanc. [Eoc.] ; jAlectona, 

 Crtr. [Eoc.]. FAMILY 2. ISPIRASTRELLIDAE, R. and D. Microscleres, 

 euasters, or streptasters usually accumulated to form an ectosomic crust. 

 Megascleres, tylostyles, or styles ; occasionally diactinal. Genera Hyme- 

 desmia, Bwk. ; Xenosponyia, Gray ; jSpirastrella, O.S. [Eoc.] ; jLatrun- 

 culia, Boc. [Eoc.] ; Sceptrintus, Tops, FAMILY 3. POLYMASTIIDAE, Vosm. 

 Without microscleres ; cortex differentiated ; skeletal framework radiate. 

 Genera Polymastia, Bwk. ; Trichostemma, Sara ; Rhaphidorus, Tops. ; 

 Proteleia, R. and D. ; Tylexocladus, Tops. ; Sphaerotylus, Tops. ; Quasilina, 

 Norm.; Ridleia, D. ; Tentoriam, Vosm. ( = Thecaphora, O.S.), (Fig. 31). 

 FAMILY 4. ISUBERITIDAE, Vosm. No microscleres ; no differentiated cor- 

 tex ; framework not radiate ; megascleres nearly always tylostyles. Genera 

 jSuberites, Ndo. [Eoc.] ; Ficulina, Gray ; Laxosuberites, Tops. ; Terpios, 

 Duch. et Mich. ; Pseudosuberites, Tops. ; Prosuberites, Tops. ; Rhizaxinella, 

 Keller ; Semisuberites, Crtr. ; Axosuberites, Tops. ; Poterion, Schlegel. 



ORDER 2. fHalichondrina, Vosmaer. 



Typically non-corticate ; skeleton usually reticulate ; microscleres 

 monaxon (sigmata chelae, toxa, microrhabdi), very exceptionally polyaxon 

 (euasters in some Axinellidae). 



FAMILY 1. fHAPLOSCLERiDAE, Tops. ( = HOMORRHAPHIDAE, R. and D. 

 + HETERORRHAPHIDAE, R. and D., pars). Spiculation of a simple type, 

 very often with diactinal megascleres alone ; microscleres, if present, never 

 chelae. SUB-FAMILY (a). ICHALININAE, O.S. Skeleton composed of fibres 

 of spongin enveloping diactinal megascleres ; the latter often greatly 

 reduced in size and quantity. Microscleres usually wanting. Genera 

 jChalina, Grant [Eoc.], (Fig. 34) ; Pachychalina, O.S. ; Siphonochalina, 

 O.S. ; Acervochalina, R. ; Toxochalina, R. ; Chalinula, O.S. ; Spinosella, 

 Vosm. ( = Tuba, Duch. et Mich.) ; Cacochalina, O.S. ; Sclerochalina, O.S. ; 

 Ceraochalina, Keller. SUB-FAMILY (6). IRENIERINAE, O.S. Skeleton of 

 spicules sometimes with a confused arrangement, sometimes forming a more 

 or less regular network. Spongin wanting or present in small quantities, 

 seldom enveloping the spicules completely. Genera jHalichondria, 

 Fleni. [Eoc.]; ^Reniera, Ndo. [Eoc.]; Petrosia, Vosm.; Metschnikowa, 

 Grimm ; Pellina, O.S. ; Eumastia, O.S. ; Reniochalina, Ldf. ; Gellius, 

 Gray ; Rhaphisia, Tops. ; Menanetia, Tops. ; Astromimus, Ldf. ; Damiria, 

 Keller. SUB-FAMILY (c). ISPONGILLINAE, Gray. Fresh water sponges, 

 for the most part similar to Renierinae. SECTION a. IEUSPONGILLINAE 

 ( = SPONGILLINAE, Crtr.). The gemmule, so far as it is known, lacks a coat 

 of special spicules. Genera jSpongilla, Lam. [ Jur.], (Fig. 3 3) ; Lubomirskia, 

 Dyb. SECTION ft. MEYENINAE, Vejd. The gemmule, when present, has 

 an envelope containing special spicules. Genera Trochosponyilla, Vejd. ; 



