THE SPONGES. 53 



very slightly toward the apex, there becoming suddenly rounded or 

 pointed, and are densely covered with short, sharp spines. Basal diameter 

 of the ray excluding the spines, which are 1-2 fx high, is about 5 [x.. The 

 rays are equal or subequal in length; total diameter of the spicule, 100- 

 160 fj.. A direct comparison with preparations of B. levis shows that in 

 the latter species the stauracts are much less strongly spinose than in 

 the form here described. 



In the autogastral hexacts, Fig. 2, Plate 6, the rays are straight or 

 slightly curving, the distal ray commonly more distinctly curved than the 

 others. The tangential and proximal rays bear very small, sharp spines. 

 The distal ray, which is longer than the others, bears longer spines, many 

 of which project upwards. The tangential and proximal rays taper evenly 

 to points ; the distal ray is cylindrical, then tapering. All rays have » 

 basal diameter of about 4 /x. Length of the distal ray, 110-140 /xj length 

 of the proximal and tangential rays, which are subequal, 60-90 /x. 



Schulze (1902, p. 80) mentions that in B. levis the spines on the distal 

 ray of the autogastral hexact are often slightly different from those on the 

 other rays. On the other hand, in the form here described, spicules occa- 

 sionally occur in which the 6 rays are equally long. 



The oxyhexasters, Fig. 12, Plate 5, are 80-100 /a in diameter. The 

 smooth principals are 4-6 fx long. The delicate, roughened terminals, of 

 which there are 2 or 3 to a principal, diverge strongly, are slightly curved, 

 and taper evenly to points. 



In the hypodermal pentacts all rays are smooth, tapering to points 

 which are not very sharp ; no trace of the distal ray. The px'oximal my, 

 which passes more than halfway through, often nearly through, the 

 sponge wall, is 1.0-1.7 mm. x 30 yu, ; frequently accompanied by 2 or 3 

 diacts. The paratangential rays are 340-500 /x x 24 /i, overlapping and 

 forming a meshwork, with meshes 340-500 /x in diameter. 



The ends of the diacts are pointed, or rounded and often enlarged ; 

 roughened with microtubercles, which may cover the entire end or be 

 restricted to a subterminal area. The slender diacts are commonly pointed 

 and not enlarged at the ends, and are nearly cylindrical. The larger 

 diacts obviously taper from the middle toward the ends. The diacts vary 

 in length from 1 to 15 mm., in thickness from 7 to 60 /a. While most of 

 them lie parallel to the sponge surfaces, numerous slender ones and the 

 scattered large prostalia pass obliquely or radially through the wall. As 



