PORIFERA. II. 



J 57 



oscular side, they are here gathered to bands running to the top of the cone, and the cone being, as 

 it were, a little twisted, the mentioned bands get a somewhat spiral course. 



The skeleton. The dermal skeleton. In the dermal membrane of the pore side no horizontal 

 spicules are found; the membrane of the oscular side, on the other hand, is provided with horizontal, 

 scattered, rather close-lying dermal spicules; on the pore side the membrane is supported by more or 

 less perpendicular pillars of dermal spicules; they spread in a penicillate way and support the mem- 

 brane, but they do not pierce it, or almost not at all. These spicules support the membrane between 

 the pores, and sometimes a few quite horizontal spicules may reach from them into the membrane. 

 On the oscular side no pillars of dermal spicules are seen, but the membrane is resting on the main 

 skeleton below, the styli of which may project a little here and there. When on the oscular side here 

 and there a group of pores is found, the membrane is in this place constructed quite as on the pore 

 side and is supported by pillars. The main skeleton is quite irregular; longer fibres are not found, 

 and meshes are scarcely to be spoken of, as the spicules more particularly convey the impression of 

 being irregularly scattered, their ends, however, are generally seen to meet. They are partly lying 

 singly, partlv in loose bundles of few spicules. In the nodes of the skeleton a distinct mass of spongin 

 is found. 



Spicula: a. Megasclera. i. The skeletal spicules are acanthostyli ; they are generally some- 

 what curved, and the curve is almost always situated near the head-end; they are evenly and rather 

 long and finely pointed. The spinulation may be somewhat varying, but is generally rather scattered, 

 and the spines are fine; they continue to the very point. At the head-end a few spines are placed 

 more close together. It is especially in the upper two thirds of the style, below the closer placed 

 spines of the head-end, that the spines are highly scattered, in the lower part they are generally again 

 closer together. The spines of the lower part are frequently directed somewhat backwards. Their 

 length is rather constant and is between 0-44 and o-5i8 mm , and the thickness is croio— o-oi28 mm . 2. The 

 dermal spicules are strongyla; they are more or less curved, more rarely straight. Their ends, 

 which may sometimes be very slightly swollen, are generally finely spined, but the spinulation may 

 become almost indiscernible, and they may also be quite smooth. They are somewhat fusiform, being 

 thickest in the middle. The two ends are not equal, one being always a little thicker than the other. 

 Their length is 0-27— o-34 mm , the thickness is 0-007 — o-oio mm . Quite few developmental forms were seen, 

 they were distinctly monactinal and showed no spines, b. Microsclera ; these are of only one form, 

 chelse arcuatse; they resemble the chelse of the preceding species, but are finer, and their terminal 

 parts are not recurved. The tooth is elliptical, broadest below and of the same length as the alae; 

 the lower edge of the alse is not much indented, and therefore they have no tooth-like appearance, 

 in this respect the chelse approach the palmate chelae. The length is 0028— o-034 mm , and the thickness 

 of the shaft is ca. o-oo2 mm . The chelae are found throughout the sponge, but especially in the dermal 

 membrane. 



As I have examined a piece of Fristedt's type specimen, I have been able to identify the 

 species with certainty. It seems to be closely allied to the preceding one, but all three forms of 

 spicules show distinguishing characters. 



