46 PROCEEDINGS OF THE NATIONAL MUSEUM vol.81 



The dermalia are nearly smooth pentactins. The rays vary from 

 IQOfi to 190/A in length, as measured from the center, and are 16/* thick 

 at the middle. They taper outward slightly, or not at all, and end 

 somewhat rounded or exjDanded. The paratangential cross is usu- 

 ally — but not always — slightly convex, as the rays themselves. On 

 the surface, the dermal latticework presents irregular meshes, though 

 in places these show a tendency toward an irregular quadrate ar- 

 rangement. All the rays are nearly smooth on the surface, except on 

 the thickened, rounded end, which is covered with densely distributed 

 tubercles. 



The gastralia are also pentactins, though they are somewhat 

 different in shape and size from those of the dermalia. The para- 

 tangentials measure 180/^ to 200fx in length, while the proximal un- 

 paired ray is somewhat longer, measuring 200/a to 250/x. All the rays 

 are quite straight, not arched convexly as in the dermalia, and grad- 

 ually attenuated toward the conically pointed and roughened ends. 



Scopulae are represented by two kinds, one being a larger, robuster, 

 and much more abundant form than the other. It has four terminal 

 branches, which lie between the proximal radial rays of the dermal 

 hexactins and nearly reach the surface, arising from an inconspicu- 

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

 of each branch is uniformly thick, sparsely covered with microspines 

 and slightly divergent outward. Toward the end, branches are 

 thickened in a spherical knob-shaped manner. It is also densely 

 covered with spines, large and distinct at the base, directed back- 

 ward, and smaller toward the distal convexed surface. The shaft is 

 generally simple, straight, SOO/i, to 400/x long, and gradually attenu- 

 ated toward the pointed and roughened end. 



Of the other kind of scopulae, two to four branches also project 

 at the tip of the shaft ; but they are different from the scopulae de- 

 scribed above, as follows : The distal thickening of the shaft is very 

 prominent, nearly spherical, and the two to four branched rays arise 

 from its margin and diverge somewhat prominently outward. They 

 are nearly cylindrical, measuring 30/^ to 40/1 in length, somewhat thin 

 at the base, and gradually thickened at the end. They terminate in 

 a small spherical knoblike swelling densely covered with microspines 

 which are larger at the base and directed backward. 



The onychasters are fairly numerous in the choanosome. They are 

 slender rayed and rather small, 40/* to TO/* in diameter. Each short 

 principal bears two or three, sometimes four, terminals, which are 

 widely divergent, quite straight, thickest at the base, and gradually 

 thinned out toward the end. They are quite smooth on the surface. 

 The tip carries two fine prongs. Unlike the claws in a true ony- 

 chaster, these are generally directed obliquely forward and outward. 



