500 



REVISION OF THE AXINELLIDiE, ii., 



B.truncata Hentsche](i3), which (having a spiculation composed, 

 in the case of the first, of subtylostyli, sigmata, and toxa, and 

 in the others, of tylostyli and sigmata) must be transferred to 

 Tylodesma. In order to frame a satisfactory definition of 

 Biemna, which will serve effectually to distinguish it from 

 Dragmacido7i and Rhaphoxya (gg. nn.), it is necessary to insist 

 upon the presence of sigmata as an essential character of the 

 genus : for this reason, if for no other, Topsent's Desmacella 

 aherrmis (with trichodragmata alone as microsclei'es), which 

 Lundbeck has I'eferred to Biemna, must be removed therefrom: 

 and for its reception I propose a new genus, DragmateUa, which 

 I provisionally regard as occupying a position between Dragma- 

 cidon and Rhaphoxya. Lundbeck is inclined to refer also 

 Schmidt's imperfectly known Desmacella vayabunda and D. 

 pnmilio to Biemna. Of these two species I have not seen the 

 descriptions; but judging from Schmidt's original diagnosis of 

 Desmacella, quoted by Ridley and Dendy(83), the microscleres 

 present are sigmata and (or) toxa, in which case the species 

 cannot in my estimation be assigned to Biemna, but belong most 

 probably to Tylodesma. As regards Kieschnick's Desmacella 

 fragilis, referred to above, it is impossible, owing to the un- 

 reliability of its description, to express any definite opinion. If 

 it be true that its microscleres are sigmata, trichodragmata, and 

 toxa, as stated, I think that this would render necessary the 

 erection for it of a new genus; until rediscovered, however, the 

 species must be regarded as incertce sedis. 'J'he only other species 

 about which there can be said to exist any occasion for doubt is 

 Desmacella cavernula Bowerbank(l), in which the microscleric 

 spiculation is described as consisting solely of sigmata; but as 

 the megascleres are styli (and not tylostyli), and, furthermore, 

 as there is ground to suspect, owing to the dried condition of 

 Bowerbank's single specimen, that the occurrence of tricho- 

 dragmata therein was overlooked, the probability is that the 

 species is correctly to be assigned to Biem,na. Nevertheless, the 

 species is peculiar, regarded as a member of this genus, in the 

 fact that the megasclei^es are distinguishable into two groups, 

 the one kind composing the fibres, the other occurring inter- 



