636 REVISION OF THE AXINELLIDiE, iii., 



and to distribute the remaining species among three new genera, 

 — Dragma.via, Dragmacidon, and Axidragma. Forms capable 

 of being referred to Thrinacophora in the preAaously understood 

 sense would result from any of the genera Biemna (sens, ampl.), 

 Sigmaxinella and Sigmaxia by the loss of sigmata, but with the 

 possible exception of those I ascribe to Dragmacidon (which, if 

 provided with sigmata, would perhaps require to be included in 

 Biemna), none of the known species appear to have been thus 

 derived. 



Thrinacophora as here defined comprises, at present, five 

 species, viz., T . fiiniformis Ridley tfc Dendy, T. spinosa Wilson,! 

 2\ incrustans Kieschnick(23), T. cervicornis Ridley & Dendy, and 

 7\ rhaphidophora Hentschel. Kieschnick's species — if its ex- 

 tremely meagre description is to be relied upon, — has essentially 

 the same spiculation as that of the type-species, and, if such be 

 the case, must of necessity be included in the genus, notwith- 

 standing its being of encrusting habit; in the face of what has 

 been disclosed by Thiele(41, p. 935), however, it is questionable 

 whether this species has any real existence. The remaining four 

 species, in spite of their many points of agreement, ai'e extremely 

 well distinguished, and, indeed, might almost be regarded each 

 as the type of a separate genus; since, however, their resem- 

 blances appear to be due to genetic relationship, their retention 

 in a single genus has most to recommend it. 



It is exceedingly doubtful if the species referable to Thi-ina- 

 cophora, in the restricted sense, belong properly to the Axinellidtie 

 at all. In spiculation they pi'esent many striking points of 

 analogy with the genera Raspailia, Syringdla, A.rechinaiiS), 

 Axiai7ion(i3), and Trikentrion, — the significance of which is greatl}^ 

 heightened, in the case of the last-mentioned two genera, by the 

 fact that, in Trikentrion, microscleres are sometimes present in 

 the form of trichodragmata and the peculiar acanthostylote mega- 

 scleres characteristic of the genus are sometimes very scarce, and 

 by the fact that, in Axiamon, the dermal megascleres are spined 



t H. V. Wilson, Jiulletin of the United States Fish Commission, Vol. 

 XX., Pt..2, 1900, p. 400, 



