E. KOMEYAMAT.— GEX. CHARACTEES. 255 



general dermal surface. The cuflf is therefore thick at its base 

 and becomes thinner towards its free, outer edge. 



From this edge there spring fortli thin and inconspicuous 

 prostal needles of various lengths, forming a palisade-like, but 

 irregular and much interrupted row. The longest of them may 

 project to a length of G nun. They have, as already mentioned, 

 rough surfaces. 



The parietal oscida (PL IX, iigs. 1, 2, 4) are round, 2-3';'.2 

 mm. iu diameter ; each bordered by a thin, iris-like membrane. 

 They are tolerably uniformly distributed in right and left handed 

 oblique rows. In the middle part of the sponge, they are situated at 

 intervals of <">-18 mm. or more ; near the ends, more closely together. 



The external mrfaec of the lateral wall may be said to be 

 undulating on account of the low, flat and disconlinuous swelling 

 of the spaces between the parietal oscuhi. The swelling is by 

 far too inconsiderable to be called a ledge, but culminates in irregu- 

 larly conical or compressed elevations which are again small and 

 never of any conspicuous height. Their summits, lying at intervals 

 of 9-14 mm. from one another, bear each a group of thin, rough- 

 surfaced proslalia lateralia before referred to. These project to a 

 maximum length of about 10 mm., and are arranged, iu groups of 

 only a very few or at the most of several together, in either closely 

 adheient or diverging tufts. Otherwise, as when they spring from 

 along the edge of a compressed prominence, they form a short row. 



The entire external surface is covered with a delicate, 

 quadrate-meshed, dermal lattirework formed of exceedingly fine 

 beams (PI. IX, fig. 4). The sides of the meshes measure not 

 more than 0.4 mm. in length. Each nodal point of the lattice- 



