HYALASCÜS SIMILIS. 103 



work as that ünardins: tlie entrance into the main canal on the 

 gastral surface. In other Avorcls, the lining layer of the gastral 

 cavity is duplicated on the wall of the main passage of excurrent 

 canals. But this duplication does not occur in all the smaller 

 canals. 



It must be said that in respect of the wall- structure raacro- 

 scopically considered, the sponge shows a rather wide deviation 

 from both //. sagamiensis and //. sinnlis. Nevertheless, there 

 exist several points of close resemblance in spiculation, a fact 

 which mainly weighed with me in referring the species to the 

 same genus. The species is probably very nearly related to 

 Crateromorpha ; but I was deterred from placing it under that 

 genus solely by the presence of hexactins among the dermalia 

 and of a covering latticework to excurrent canalar apertures and 

 by the fact that the gastralia are all hexactins. 



Spiculation. 



The parenchymalia are exclusively slender diactins of widelv 

 varying sizes. The largest, the principalia, may reach 23 mm. 

 in length and 175 !'- in breadth at the middle, while the finest 

 are of the ordinary dimensions of a comitalia only about 7 // 

 thick. They are in general irregularly bent or wavy, either 

 gradually tapering out to a point at both ends or terminating 

 with conical or rounded tips. Subterminally the surfece seems to 

 1)e always rough on account of microtubercles that are sometimes 

 wart-like and sometimes spine-like. As a rule there exists not 

 the slightest trace of an external swelling marking the spicular 

 center. 



Both the hypodermal and hypogaüral beams (PI. VIII., 



