36 PROCEEDINGS OF THE NATIONAL. MUSEUM vol. 81 



of the same spicule may be divided into two short terminals while 

 the other principals are not divided at the end. From this form, 

 I can ascertain that the oxyhexaster of the present species may be 

 derived from the small hexactin, though the latter is not found in 

 this sponge, Oxyhexasters measure 40/i. to YO/a in diameter; the 

 terminals are 8fx to 12/j, long, and the principals are twice as long 

 as the terminals. 



Besides the uncinates and the oxyhexasters, the parenchymalia of 

 the present species contain many simple hexactins and pentactins of 

 much larger size, though they occur abundantly on subdermal regions 

 and are sometimes nearly absent in the parenchyme. 



Most of the hexactins (fig. 5, &) measure IGO/x to 240/x in axial 

 length ; their rays are gradually attentuated to sharply pointed ends. 

 The surface of the rays is slightly roughened. These spicules are 

 sparsely distributed in the parenchyme, though much more abun- 

 dantly in regions between the dermal pentactins. The pentactinic 

 form appears rarely, intermingling with the former, and exhibits 

 nearly the same structure as the hexactins. 



The dermal membrane is supported by the four rectangularly 

 intersecting tangential rays of the pentactins (fig. 5, a), whose 

 unpaired proximal ray penetrates into the parenchyme vertically. 

 Though the proximal ray is always perfectly straight and gradu- 

 ally narrowed into a conical form toward the pointed end, the four 

 paratangential rays are frequently bent gently inward. Infre- 

 quently they are straight and end in a conical point. All the sur- 

 faces are roughened; and toward the ends of the rays the micro- 

 spines increase in height and are more densely placed. The proximal 

 ray usually does not exceed the tangential in length, measuring 

 200/x to 350/x in length and 30/* broad at the base. It is always 

 cylindrical and somewhat smooth at a short distance from the base, 

 with the exception of a strongly roughened end. The tangential 

 rays are also cylindrical and usually somewhat longer, measuring 

 230/1 to 380/x in length. The roughness of the surface is quite similar 

 to that of the proximal ray. 



The opposed tangential rays of these pentacts in the dermal mem- 

 brane form a nearly quadratic framework. Frequently, also, they 

 are irregularly arranged. 



The gastral pentactins agree essentially with the dermal; so that 

 1 may simply refer to the above description of the latter and note 

 only that the principal deviations are a somewhat smaller size and 

 a somewhat less regular arrangement. 



Discohexasters seem to be of two kinds, which are designated by 

 the letters A and B. Form A (fig. 5, c) appears commonly in 

 subdermal and in subgastral regions, and infrequently in the 



