634 



A REVISION OF THE GENERA WITH MICR0SCLERE8 

 INCLUDED, OR PROVISIONALLY INCLUDED, IN 

 THE FAMILY AXINELLID.E ; WITH DESCRIP- 

 TIONS OF SOME AUSTRALIAN SPECIES. Part iii. 



[porifera.] 



By E. F. Hallmann, B.Sc, Linnean Macleay Fellow of 

 THE Society in Zoology. 



(Plates xxix., figs.3, 5, 6; xxxiii., fig.6; xxxviii., figs.5-9; xxxix., 

 figs.1-5; xL, figs.1-4, xli.-xliv.: and Text-figs. 17-20.) 



Genus Thrinacophora Ridley. 



Definition. — Axinellidjv typically of ramose habit, perhaps also 

 sometimes encrusting or massive, with even or conulose surface, 

 and a skeleton consisting (in the ramose forms) of a dense central 

 axis from which paucispicular fibres (in some species reduced 

 to single spicules) radiate to the surface. Megascleres of at least 

 three kinds: (i.) comparatively short oxea, typically occurring 

 chieriy or only in the central axis; (ii.)long, setaceous styli, 

 composing the radial fibres; and (iii.) monactinal, sometimes 

 apically pronged, dermal megascleres forming surface-tufts or 

 lying in the dermal membrane tangentially, but not necessarily 

 confined to the ectosomal layer exclusively. In addition, oxeote 

 or strongylote modifications of one or both kinds of the mon- 

 actinal megascleres are commonly present. Microscleres : tricho- 

 dragmata, accompanied or not by singly scattered trichites. 



Type-species, T. funi/ormis Ridley ct Dendy. 



Originally founded by Ridley(32) to designate the peculiar 

 T. funi/ormis, and conceived as being essentially characterised by 

 the possession of dermal megascleres in the form of " clado- 

 strongyla," the genus Thrinacopho7-a was next modified by Ridley 



