BY E. F. KALLMANN. 401 



lengtli which, usually exceedino 900/a, ranges from (rarely less 

 than) 500/A up to 1 200 /x (ii) Small tylostyli; composing the cor- 

 tical skeleton and scattered in the choanosome; as a rule, slightly 

 curved; 80 to 135/x long-, and seldom as much as 4-5/x in diameter, 

 (iii) Larger tylostyli; occurring- only in the choanosome; closely 

 resembling the preceding in shape, and possibly connected with 

 them by intermediate forms; 145 to 210/x in length, and up to 1 n 

 in diameter. 



It remains to be mentioned, that the type-specimen of Polymas- 

 tia zittelii bears a likeness so extremely close to the figure given in 

 the Catalogue (PI. ii., fig. 2), with the title Sideroderma navicelli- 

 gerum R. & D., as to enable, one to say, with the utmost posi- 

 tiveness, that the original of the figure actually was a specimen of 

 P. zittelii. Moreover, I am inclined to doubt, on the evidence avail- 

 able, whether Lendenfeld really had a specimen of Sideroderma 

 navicelligerum at his disposal. The only specimen in the Aus- 

 tralian Museum bearing Lendenfeld's label certifying it to be one 

 identified by him as such, namely, a specimen labelled "Desmacidon 

 polymastia^' (wiiich name is given in the key-list as the MS. syno- 

 nym of S. navicelligerum), is found to be an example of a new 

 species of Histoderma — H. actinioides {vide Appendix). This 

 exhibits so many analogies with S. navicelligerum as to render 

 quite possible its having been mistaken for that species, at any 

 rate by so careless an observer as Lendenfeld was at the time of 

 writing the Catalogue; and, moreover, there is reason to believe 

 that Lendenfeld did not examine his "Sideroderma navicelli gerum" 

 very critically, since his description of it, practically word for 

 word, even to the minutest details regarding the spicule-measure- 

 ments, is copied from Ridley and Dendy's preliminary account of 

 S. navicelligerumiSi). But most remarkable to relate, in connec- 

 tion with this specimen, labelled "Desmacidon polymastia/' is the 

 fact that it is figured in the Catalogue (PI. iv., fig. 1) as an ex- 

 ample of Stylotella polymastia! 



Taking everything into consideration, I think we are justified in 

 regarding Lendenfeld's Sideroderma navicelligerum as a s>iion>Tii 

 of Histoderma actinioidjes. 



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