A. AMPHIDISCOPHORA. 



I. HYALONEMATID^. 



Of the 120 Hexactinellida collected by the "Investigator" a considerable 

 number of specimens and of species belong to the Amphidiscophora, a group 

 characterised and distinguished from the other Hexactinellida (HeMisterophora) 

 by the presence of amphidiscs and the absence of hexasters. Having united 

 Foliopogon Wyv. Thoms. with Pheronema Leidy, I distinguished in the only 

 family of the Amphidiscophora, the Hyalonematidse, the three genera Pheronema 

 Leidy, Hyalonema J. E. Gray, and Semperella J. E. Gray. Further investi- 

 gations have however shown me the advisability of re-establishing the genus Polio- 

 pogon as distinct from Pheronema (see below). To these four the new genus 

 Lophophysema, based on a fine specimen of the " Investigator " collection, is to 

 be added, so that the family now comprises five genera, Pheronema Leidy, Polio- 

 pogon "Wyv. Thoms., Hyalonema J. B. Gray, Lophophysema F. B. Sch., and /Sem- 

 perella J. E. Gray. All these with the exception of Poliopogon are represented 

 in the " Investigator " collection. 



The two subfamilies Hyalonematinas and Semperellinx have nearly the 

 same spiculation and are only distinguished by their external shape and the 

 formation of their canals. This distinction appears so unimportant that I now 

 refrain from distributing the genera among them. 



Pheronema, Leidy. 



Among the first " Investigator "-Hexactinellida received were two speci- 

 mens of a new Pheronema species which I described as P. raphanus in the 

 Abhandl. der Preuss. Akad. 1894, pp. 8-13. Both had completely lost their 

 prostalia lateralia and I thought that their absence was a peculiarity of this 

 species. Formerly, in the " Challenger " Report, I had distinguished the allied 

 genera Pheronema and Poliopogon by the presence of prostalia lateralia in the 

 former and their absence in the latter. Now finding a sponge iindoubtedly 

 belonging to Pheronema and, as I then believed, without prostalia lateralia, 

 I thought it necessary to unite these two genera.* The material of Pheronema 



* Abh. Preuss. Ak., 1894, p. 7. 



