HYALONEMA (OONEMA) DENSUM. 343 



inclined and curved concave towards the tip of the ray. The largest spines 

 usually attain a length of about 27 m- The maximum diameter of the distal 

 ray, together with the spines, is 32-85 y.. The lateral rays are 40-77 ^ long, 

 nearly cylindrical in their proximal, and conical in their distal part. Their 

 middle and sometimes also their proximal parts bear broad and low spines. 

 The end-parts are smooth and sharply or bluntly pointed. 



The sinall dermal pinnies are similar to the large ones. They are nearly 

 always pentactine. Exceptionally a remnant of a proximal ray, sometimes 

 15 IX long, is present. The distal ray is straight, 230-505 ^ long, most frequently 

 about 370 m, and 6-10 m thick at the base. Its maximum diameter, together 

 with the spines, is 12-47 //. The lateral rays are 40-68 /x long. 



The gastral pinules (Plate 95, figs. 2, 11-14, 16-18). Although the length 

 frequency-curve of the distal rays of these spicules is irregular and exhibits no 

 less than five elevations, these are separated by depressions so shallow that 

 differently sized kinds of gastral pinules cannot be distinguished. The gastral 

 pinules are generally pentactine, rarely hexactine. The hexactine forms are, 

 however, not so rare among these pinules as among the dermal. Apart from 

 this the gastral pinules are quite similar in shape to the dermal. The distal 

 ray is straight, 300-930 /x long, most frequently 400-650 ix, and 10-28 /j. thick 

 at the base. Its maximum thickness, together with the spines, is 25-80 n. 

 The spines are sometimes 35 m long. The lateral rays (Plate 95, figs. 11, 12) 

 are 35-82 m long. The proportion of the length of the distal to that of the 

 lateral rays of the same spicule is 7-13 to 1, on an average 9:1. The proximal 

 ray, when present, is, in shape and spinulation, similar to the laterals and 20- 

 68 M long. 



The scarce canalar pinules are mostly pentactine. The distal ray is 150- 

 200 M long, and 7-10 m thick at the base. Its maximum transverse diameter, 

 together with the spines, is 12-22 ix. The lateral rays are 50-60 yu long. 



The hypodermal and hypogastral pentactines are very similar. Both have 

 a straight, conical, terminally rounded proximal ray 540-860 /a long, and 20-48 m 

 thick at the base. The lateral rays are also straight, conical, and rounded. 

 Those of the same spicule are often very unequal in size. Their length is 250- 



530 m. 



The hexactine megascleres are 1.1-3.5 mm. long and 1.1-1.8 mm. broad. 

 In the larger, two opposite rays are longer than the other four. In the smaller 

 the six rays are usually fairly equal in size. The rays are 40-90 m thick at the 

 base, straight, generally regularly conical, and rounded at the end. Occasion- 



