BY E. VON LENDENFELD, PH.D. 313 



undermining the skin (Plate XXXII., fig. 21). The canals are 

 depressed radially. The outer side is flat and forms a plane parallel 

 to the outer surface. Below the outline of these canals is very 

 irregular, forming wide, conic or trumpet shaped extensions 

 which lead into the inhalent canals. The average width of this 

 subdermal cavity is only 0-03 mm. 



The inhalent canals are much curved and only slightly ramified. 

 Their transverse section is generally more or less circular and 

 their diameter averages about 0'18 mm. 



They are accordingly very much wider than the subdermal 

 cavity. The ramifications are irregular. Divided from the system 

 of inhalent canals by a lamella, 0-045 — 0'05 mm. in thickness, we 

 find the exhalent canals. These are much more irregular in shape 

 than the inhalent ones (compare the figure), and of similar average 

 width. Also these are only slightly and irregularly ramified and 

 unite to form irregular lacunose cavities, the oscular tubes. (Plate 

 XXXII., fig, 21.) The average diameter of these spaces is 

 0'6 — 0"8 mm. Towards the circular oscula, which are not raised 

 above the surface and scattered irregularly all over the sponge, 

 the cavities ai'e constricted. The diameter of the osculum is 

 0-12 mm. 



The ciliated chambers are spherical and very similar to those 

 described above of Halme Nidus Yesparum. They form like those 

 of Halme a dense layer taking up the whole of the thickness of the 

 lamellae which divide the inhalent from the exhalent canals. They 

 are accordingly much larger than those of Halme, measuring 

 0"04 mm. in diameter. 



Skeleton, 



As the reader will have seen from the description of the genus 

 the skeleton of this sponge is very remarkable. (Plate XXXIII., 

 fig. 22.) The whole skeleton consists of a regular network of 

 solid hoi'ny fibres which do not contain any foreign bodies. Main 



