44 PROCEEDINGS OF THE NATIONAL MUSEUM vol.81 



The scopules are numerous and arranged perpendicularly 

 or obliquely to both surfaces ; they are rather abundant in the dermal 

 layer and are variable in shape. They usually have four branches, 

 which lie close to the center of the pentactins, where the proximal 

 unpaired ray is given off, and which nearly reach the surface. The 

 shaft is generally simple, smooth, straight, 20/x to 210)it long, and grad- 

 ually attenuated toward the pointed, roughened end. It is always 

 rough terminally, but for the rest of its length nearly smooth. 

 Though the number of branches is subject to considerable variation, 

 they are most commonly 4 in number. They arise from a compara- 

 tively short thickening at the distal end of the shaft. The basal part 

 of each branch is thin, about 52ju, long, and extends upward, bending 

 slightly outward. Toward the end it is thickened in a club-shaped 

 manner and is sparsely covered with spines, small and indistinct at 

 the base, larger toward the distal end, and directed backward. 



Uncinates, varying in length and thickness, are quite frequently 

 found close to the dictyonal honeycomb. They are arranged perpen- 

 dicularly, occasionally obliquely, to the surface and usually pene- 

 trate the whole thickness of the sponge wall. The outer half of the 

 spicule, nearer the dermal surface, is always thicker than the inner 

 half (nearer the gastral surface), which is gradually attenuated to a 

 pointed end. They are mostly 85/a long and 8ju to 15fi broad at the 

 thickest part of the outer half of the spicule. The spines projecting 

 from the entire surface of the spicule are arranged densely but 

 irregularly. 



Much more peculiar and worthy of interest are the hexasters scat- 

 tered in varying numbers irregularly through the parenchyme. 

 Their shapes and sizes differ in different regions of the same 

 individual. 



The onychasters are 45/x to 55yu, in diameter. From each short 

 principal there arise three or four thin, tapering, nearly straight, 

 considerably divergent terminals. The terminations of the branch 

 ray bear a verticil of fine claws, usually four in number. These 

 are of small size, and subject to little variation. The claws are hori- 

 zontal to the branch raj^ or extend obliquely downward, and are 

 slightly recurved. Sometimes, perhaps less often, they extend 

 obliquely upward at the end of the terminals. These probably are not 

 senile structures, as they are produced in all hexasters of the present 

 species and are undoubtedly derived from the oxyhexaster by the 

 transformation of the extremities of the terminals. 



True oxyhexasters occur more abundantly than the former ony- 

 chasters, and the latter may be easilj^ overlooked unless a special 

 search be made for them. Sometimes it was difficult to find even 

 a single onychaster between the numerous oxyhexasters; sometimes 



