HYALONEMA (HYALOXEMA) POLYCAULUM. 203 



Their inclination towards the tip generally increases uniformly towards the end 

 of the ray. The individual spines are conic, pointed, and curved more or less, 

 generally concave towards the tip (Plate 54, figs. 35, 40), sometimes in the 

 opposite direction (Plate 54, fig. 38, the lowest) and occasionally in an S-shaped 

 manner (Plate 54, fig. 39). The largest spines are 15-24 n long and 2.5-4 /u 

 thick at the base. The maximum thickness of the distal ray, together with the 

 spines, is 24-40 yu. The lateral rays are blunt-pointed or terminally rounded 

 and 24—40 n long. They bear rather sparse, conspicuous spines. The proximal 

 ray does not, when present, exceed the lateral rays in length. 



The gastral pinules (Plate 54, figs. 41-45) are also usually pentactine; hexac- 

 tine forms are, however, not so rare among them as among the dermal pinules. 

 The distal ray is 110-133 ^ long and 6-9 ju thick at the base. It is straight, 

 simply conic throughout, or cylindrical basally and conic distally, or very slightly 

 thickened below the middle of its length. It ends with a slender and very sharp- 

 pointed terminal cone, 20-35 n long, and 3-5 ^ thick at the base, that is at the 

 point of insertion of the uppermost spine. Nearly the whole of the distal ray, 

 with the exception of the terminal cone, is spined; a spineless basal region being 

 absent altogether, or quite insignificant. The spines are sparse. The largest 

 arise from the middle-part of the ray. From here they decrease in size both dis- 

 tally and proximally. The basal spines are vertical or slightly inclined, either 

 towards the tip or the base of the ray. Distally they become more and more 

 inclined towards the tip of the ray. The individual spines are conic, sharp- 

 pointed, straight or slightly curved, either uniformly concave towards the tip 

 of the ray, or, more rarely, uniformly concave in the opposite direction, or in 

 an S-shaped manner. The largest spines are 12-16 n long and 3-4 ^ thick at 

 the base. The maximum thickness of the distal ray, together with the spines, 

 is 25-40 M- The lateral rays are 40-60 ^ long, usually conic, sharp-pointed, and 

 in their distal two thirds or to a farther extent, often quite down to their base, 

 they are covered with somewhat sparse, conspicuous spines. The proximal ray 

 is, when present, similar to the lateral rays in shape and spinulation and has a 

 maximum length of 50 fj.. 



The pinule-like pentadines, which may be canalaria (Plate 54, figs. 34, 37), 

 have straight, conic, sharp-pointed rays, rather densely covered throughout 

 with small spines. Their apical ray is 110-135 ix long, their lateral rays about 

 65 Ai. The rays are 5-6 /j. thick at the base. 



The (hypodermal and ? hypogastral) pentactine megascleres have fairly 

 straight rays. The rays of the smaller forms are conic, very blunt-pointed. 



