THE SPONGES. 67 



enlarged. The proximal ray as a rule is shorter than the tangentials, 



often about 200 /x. long, of about the same thickness as the tangentials, 

 tapering evenly to a point above which it is roughened, elsewhere smooth 

 or with a few scattered minute prickles. 



The uncinates vary greatly in size, and exhibit the same difference 

 between the two ends which has been described for Farrea occa claviformis. 

 They extend radially or obliquely, often through the entire tube wall. 

 In the wall of the cups numerous large uncinates, commonly about 2 mm, 

 long, are found running parallel to the surface and at right angles to the 

 cup edge. 



The discohexasters are of the onychaster type, and are scanty or 

 only fairly abundant. Principal ray is 4-6 /a long ; terminal rays, 24-30 /x 

 long. The principal rays are smooth. The terminal rays are slender, 

 taper toward the apex, and are roughened ; capped by a minute disc 

 about 3 /x in diameter, which is divided into 4 or 5 claw-like teeth. 

 Spicules occur in which the roughening on the terminal ray is represented 

 by exceedingly minute prickles. Other spicules occur in which one or 

 several of the principal rays, or even all, bear but one terminal each. In 

 such spicules, a " knee " usually marks the passage of the principal into 

 the terminal, but this may not be present. 



The common form of dermal scopula, Fig. 3, Plate 8, has 3 or 

 4 distal rays, which are cylindrical, curved very slightly, covered with 

 minute sharp denticulations, and which terminate in very small, smooth 

 and rounded enlargements. The shaft at its upper end has a definitely 

 circumscribed enlargement on which the rays rest ; tapering thence to 

 the point, above which it is roughened ; elsewhere smooth. The shaft is 

 200-240 ^ long, and 4 /x thick just below upper enlargement ; rays, 40 ^ 



X 2 jM. Larger spicules are present in some abundance, in which the 



number of distal rays varies from 4 to 10. The rays measure 60 /x x 2 /a 

 to 100 /A X 3 jii, and terminate in rounded heads which are usually small, 

 about 5 ju, in diameter, but sometimes large, about 8 /n in diameter. The 

 rays are covered with very small sharp denticulations, which enlarge upon 

 the head, sometimes sufficiently to appear as recurving spines. The shaft 

 has a thickness of 6 /a and is somewhat larger than, although otherwise 

 like, that of the typical dermal scopula. 



The gastral scopulae, Fig. 2, Plate 8, have 4-6 slender distal rays, 

 70-80 fi long, which terminate in spheroidal heads. The heads bear, round 



