BY E. F. KALLMANN. 295 



specimens are low and broad, or (less frequently) more or less 

 compressed into plate-like form, and have a flattened upper 

 surface. In both forms, the oscula or the sieve-areas, as the case 

 may be, occur on the upper aspect of the sponge. There can 

 scarcely be any doubt that the form with oscula is identical with 

 Spirastrella papulosa Ridley and Dendy, although the oscula are 

 very much smaller than in the type of that species; while it is 

 equally certain that the form with sieve-areas is identical with 

 aS'. papulosa var. porosa Dendy(14) from Port Phillip. What I 

 cannot decide is whether we have to do with a single form or 

 with two distinct forms. 



The sieve-areas, which measure several square inches each in 

 extent, are free from the tubercles that occur in other parts of 

 the surface, and are usually slightly depressed below the level of 

 the surrounding surface; they are perforated by close-set circular 

 pores (measuring from 75^ to 160/x in diameter, and between 

 100 /x and 200 /x in distance apart), and thus present an appear- 

 ance very much resembling that of the pore-bearing surface of 

 certain polyporaceous fungi (e.g., Polyst ictus). Possibly it is to 

 these sieve-areas that Lendenfeld refers, when he speaks of 

 "movable membranes" by which "for the most part" the "vents" 

 are covered; but it is strange that he makes no reference to their 

 perforate or sieve-like character. Tlje " perforated membranes," 

 or " inhalant pore-sieves," which he mentions as occupying the 

 depressions between the papillae, are dift'erent, and correspond to 

 what is described by Dendy(Zoc. cit.) as a "beautiful pore-bearing 

 membrane" stretched between the "conuli." This membrane 

 has a minutely reticulate appearance, which, in some specimens, 

 is very distinct, in others scarcely perceptible; but it is not, to 

 the naked eye or even with the aid of a lens, " perforate " or 

 " porous " in the sense of " sieve-like." 



As far as I know, oscular sieve-areas in the genus Spirastrella 

 have been observed only in *S'. papulosa var. porosa. Vosmaer 

 makes no mention of the occurrence of anything of the kind in 

 any of the numerous forms of Spirastrella studied by him; nor, 

 by the way, does he comment upon their occurrence in S. papul- 

 osa var. porosa — '<xi\ omission difficult to account for, since he 



