HYALASCÜS SIMILIS. 97 



ventricose middle the breadth measures sagittally 230 mm. and 

 transversely löO mm. The body contracts towards both ends, 

 but less so above than l)elow. The oscular region, which termi- 

 nates in a thin simple edge, is outflaring to a greater or less 

 degree in different places. The osculum measures 135 mm. by 

 loO mm. in diameter, the lesser and the greater diameter in 

 relation to those of the laterally compressed main part of the 

 body being exactly reversed in orientation. The basal end with 

 irregular longitudinal ribs and furrows measures about 70 mm. 

 across. The surface of attachment to the firm substratum is in 

 several irregularly shaped patches. The wall is only al)Out 

 5 mm. thick in the middle of the sponge. The gastral cavity 

 extends at the bottom into the stalk-like basal region. 



As regards the general appearance of both the external and 

 internal surfaces, the texture and the canals, what I have said under 

 H. sagamiensis (pp. 89 & 90) is equally applicable here. The 

 similarity further extends into the spiculation so that this again 

 need not be described in detail except in regard to one point 

 which constitutes the chief, if not the only, distinctive character 

 of the present species. 



The point in question concerns the discohexaster (text- 

 figure 4). This occurs not uncommonly in scattered distribution 

 throughout the parenchyma, though by no 

 means so abundantly as the oxyhexasters. Being 

 of very inconspicuous appearance, a careful ex- 

 amination of the preparations is necessary in 

 order to find one. Moreover, the exceedingly 

 fine terminals easily break off, as that it is 



Text-fi^ire 4. 



„,,,., , usual to find the discohexaster in a more or less 



ilie discohexaster 



of i/. «w//«. 500 X. çiamaged condition and not infrequently repre- 



