446 



sultats des camp. scient, du Prince de Monaco, Fasc. H, 111) 

 divided Carter's genus Plumohalichondria in two genera, one 

 with the fibres formed of smooth, diactinal spicules, echinated 

 by spined spicules, and the other with the fibres formed of 

 spined, monactinal spicules and echinated by similar spicules. 

 For the first genus, with the fibres formed of smooth, diactinal 

 spicules, be maintained Carter's name Plumohalichondria, 

 but unfortunately he placed Carter's type of the genus, P. 

 microcionides in the other genus; evidently he had not exa- 

 mined this species, and thus he mistook it as having the fibres 

 formed of spined styli, while it in reality has them composed 

 of long, smooth oxea; as a consequence the genus with the 

 fibres formed of smooth, diactinal spicules must have the name 

 Plumohalichondria Cart., with the type microcionides Cart. 



To the other genus, with the fibres composed of spined 

 styli, Top sent gave the name Stylostichon, and as he at the 

 same place described a new species S. Dendyi, 1 se no reason 

 why this should not be the type of his genus, to which also 

 plumosum Mont, and frondosum R. and D. seem to belong. 

 Thiele (Arch, für Naturgesch. 1903, 387) declares, that Top- 

 sent's genus Stylostichon can only be a synonym to Plumo- 

 halichondria, as he placed the type of this, microcionides in 

 Stylostichon, but asTopsent, as said, at the same time de- 

 scribed the species Stylostichon Dendyi, I do not se why his 

 simple mistake with regard to the species microcionides should 

 cause his genus to fall; on the contrary it seems natural, 

 that when microcionides is removed from Stylostichon to Plumo- 

 halichondria, the former genus stands with the type Dendyi. 



In the place quoted Thiele thinks it not necessary to 

 divide the old genus Plumohalichondria, but I think the dividing 

 character, Ihe difference in the spicules composing the fibres, 

 is of no small value. Thiele seems also to think only on the 

 species microcionides and mammillata Cart. = incrustans Cart., 

 and both these species have the fibres formed of smooth diac- 



