96 



PORIFERA. I. 



small ones o-oo8—o-or"""; rhaphides of two sizes, mosf frequnitly in drngiiiata. f/ir lovg ones o-2jj 

 — 0-268""". tlic siiori ours iroS — o'l"'"'; comviata o-oo8""". 



The only specimen in hand of this species has an open, somewhat irregular calicnlar form, 

 and has been attached without any stalk. Its height is ca. G"^™, and its greatest breadth in the circum- 

 ference ca. 8'5''"', while the thickness of the wall is scarcely 2""". The surface is set witli small processes 

 due to the ends of the fibres. The colour (in spirit) is pale yellow. Tlie consistency is less firm than 

 in the preceding species. The drrinal iiinnbraiie is thin, and is supported b\- the ends of the fibres; 

 of spicules it has only microsclera, viz. rhaphides of two sizes, paitly scattered in the skin, partl\- oc- 

 curring in bundles, and small sigmata, present in very large numbers. In some places of the skin was 

 seen a similar structure with thinner fields as in the preceding species. In the present species osctiln 

 have a quite peculiar structure their edge being provided with papillae. When the osculum is open, 

 it is a more or less round hole of a diameter of ca. 0-5""". When this is the case some slighth' pro- 

 jecting lobes are seen in the edge, and the ends of rhaphides project into the opening. When 

 the osculum is being shut these lobes grow to longer and longer papillae, and the projecting 

 rhaphides cross each other; at last the papillse come together, and the closed osculum forms a little 

 conical process (PI. VI, fig. 14). Whether the papillae are free or only papilla-like folds of the skin, I 

 have not been able to see. This way of closing the osculum is quite peculiar, and it is to be supposed 

 that the function of the projecting rhaphides is to bar the entrance when the osculum is not closed. 

 In the present specimen oscula are found abundantly on the inside; but as the skin of the outside is 

 torn off it cannot be decided, whether they have been restricted to the inside, or have been found all 

 over the sponge. Porrs I have not seen; they must be supposed to be lying in the before mentioned 

 thin-skinned fields. 



The skeleton is of a quite similar structure as in the two preceding species, and consists of 

 fibres running from the base up through the sponge branching and anastomosing, and giving off 

 branches towards the surface supporting the dermal membrane. The fibres are a little thinner, and 

 seem to be somewhat more richly branched than in the preceding species. A distinct, clear mass of 

 spongin unites the spicules of the fibres, and coats the fibres entirely, though only with a thin, scared}' 

 observable layer. 



Spicnla: a. Megasclera ; these are slightly, or at the head end, a little more strongh' curved 

 styli with an evenly tapering point the outermost part of which mav be a little more or less shortly 

 pointed. The length varies from ca. 0-94 — 1'37™", and the thickness at the upper end is 0-025 — 0'035'""'. 

 Styli with more or less broadly rounded points are not scarce. 



Also in this .species styli are found in the basal la\er, smaller than the normal ones, and 

 irregularly bent in different ways. 



b. Microsclera : i. Sigmata of two sizes; the larger are of a quite similar form as in the pre- 

 ceding species with a strong curve in the middle of the shaft and a little hook-shaped recurving of 

 the ends; they are also contort. The length from one hook to the other is ca. 0-09— o-io"'", and the 

 thickness is 0-0028™". These sigmata occur in very small number, and only quite singly, so that there 

 might be some doubt, whether they really belong to the sponge or are extraneous; as, however, the>- 



