498 REVISION OF THE AXINELLID^, ii., 



The three species, for the reception of which Dendy(7) proposed 

 the genus Sigmaxinella, agree in having both monactinal and 

 diactinal megascleres and, as microscleres, signiata and tricho- 

 dragmata, but in a number of other important respects they 

 differ very considerably; and, as already indicated, one at least 

 of them equally admits of inclusion in AUantophora or in Biemna 

 as hitherto defined. However, the first-described of the three, 

 S. aiistralia?ia, as well as several of the species which Kirk- 

 patrick(20) and Whitelegge(60) have ascribed to SigmaxineUa, 

 differ from all other known species possessing similar micro- 

 scleres, firstly in being of ramose habit, and secondly in having 

 an axially condensed skeleton. Consequently, with an amended 

 diagnosis, the genus Sig^naxinella also admits of being retained. 



The third species assigned by Dendy to SigmaxineUa — S. 

 JlabeUata — is (among the species having sigmata and tricho- 

 dragmata as microscleres) quite unique, not only as regards 

 skeletal structui'e, but also in the fact that the megascleres 

 are of two distinct kinds, viz., styli composing the fibres, and 

 elongated flexuous strongyla (and tornota) occurring inter- 

 stitially, — the latter of which are strikingly analogous to the 

 spicules of similar form characteristic of many species oiAxinella, 

 Phakellia, Acanthella, and Tragosia. Were it not for the presence 

 of sigmata, there would be no adequate reason, apart from the 

 flexuous character of the interstitial megascleres, for excluding 

 the species from the genus Z)ra^?nacit£o?i (g.n.), which in turn 

 comprises species hitherto assigned to 2'hrinacophora; whilst, if 

 both kinds of microscleres were absent, it would almost certainlv 

 have to be included in the genus Phakellia && defined by Dendy{8). 

 Being such as it is, however, the species undoubtedly deserves a 

 new genus for its accommodation, and for this I propose the 

 name Sigmaxia. 



The question whether AUantophora admits of separation from 

 Biemna is a much more difficult one, and at present cannot be 

 satisfactorily decided; for although there exists with respect to 

 skeletal structure a profound difference between the typical 

 species of the two genera, — as is very obvious from a comparison 

 of Topsent's figure of B. peachi{5i; PI. iv., fig. 3) with mine of 



