76 PROCEEDINGS OF THE NATIONAL MUSEUM vol. SI 



Oxyhexasters of normal, hemihexactinic (fig. 8, ^), and hexactinic 

 (fig. 8, j) forms are found; the two latter most commonly in the 

 choanosome and in the ectosome, as well as in the endosome. The 

 normally developed oxyhexasters (fig. 8, g^ h) are frequently met 

 within the hypoderm and occasionally in the parenchyme layer. 

 They measure 90/x to 150/* in diameter. From the slender and short 

 principals arise the two slender terminals, moderately widely 

 diverged. In the present species I have not seen the robuster larger 

 oxyhexasters that occur in A. alhatrossi, but I believe that some might 

 have been discovered, had a more extensive search been made. Fre- 

 quently, among the gastralia, the somewhat robuster oxyhexasters, 

 mentioned above, are to be found. This oxyhexaster has the same 

 dimensions, but it differs in having broader terminals and a dis- 

 tinctly microtuberculated surface. The hemihexactinic and hexac- 

 tinic forms, being quite similar to those of A. alhatrossi, are not 

 described. 



The macrodiscohexaster (fig. 8, /) is very much like that of A. 

 alhatrossl, except that it is perceptibly smaller in diameter. It 

 averages 450ja in diameter and is provided with a round central 

 sphere measuring 40/x to 45/x in diameter. 



The microdiscohexaster (fig. 8, k) is of two forms. The larger 

 one is rare in the dermal layer, while the smaller one is usually 

 jDresent in the choanosome and in the ectosome, as well as in the 

 endosome. The former is essentially similar to the macrodiscohex- 

 aster known to occur in A. mifsukurii, but has a somewhat shorter 

 diameter. It measures 75fi to 80/t and is fairly well supplied with 

 terminals, which are generally straight and unif ormiiy thick through- 

 out their length. The terminal disks are small, and each is furnished 

 with six or more minute marginal teeth. 



The smaller microdiscohexaster measures 32/* in diameter. I 

 have found this form on the whole sparsely distributed in the ecto- 

 some and in the endosome as well as in the choanosome, though 

 exceedingly rare in the latter. The principals are slender and form 

 a cross, measuring about 8/x in axial length. The terminals number 

 six to eight and measure 12/* to 13/j, in length. In the endosome, this 

 microdiscohexaster usually attains a diameter of 36/* to 40/*. The 

 terminals are also longer, measuring 16/* in length. 



I have always found the structure of the basidictyonal plate of 

 this species to be thick. The beams of this plate are entirely smooth 

 and look quite different from those of A. albatrossi, and the meshes 

 are much longer than in the latter. 



Remarks. — The other smaller specimen is a vaselike form with a 

 somewhat narrower inferior part of the body. The height and the 



