100 BATHYDORUS LAEVIS SPINOSISSIMUS. 



found besides the ordinary ones also, however, a few 220-320 n in diameter. 

 Their rays do not lie in one plane but form the edges of low obtuse pyramids 

 with quadratic bases. In consequence of this and the fact that the rays are, 

 in the same spicule, nearly equally long, the ray-length is a little more than half 

 the diameter of the spicule. The basal thickness of the rays is in the regular 

 stauractines 80-215 y.; the diameter is 4.5-9, generally 5-7 ju. The rays of the 

 giant stauractines 220-320 yu in diameter, above referred to, are 6-15 y. thick at 

 the base. The rays are generally terminally rounded and either cylindrical, at 

 the end as thick as at the base; or, more frequently, cylindroconic, at the end 

 only one to two thirds as thick as at the base; very rarely the ends are pointed. 

 In respect to the degree of attenuation towards the end the rays of the same 

 spicule are often unequal. 



The whole of the spicule is densely and uniformly covered with sharp conic 

 spines, its central part being quite as spiny as the distal parts of its rays. The 

 proximal spines are nearly vertical, the distal ones directed more or less obliquely 

 outward. Large and smaller spines are irregularly intermingled; the largest 

 are sometimes 4 n long. 



Stauractines with one or more rays reduced in length (Plate 15, figs. 5, 9, 10, 

 18, 21, 22) are quite frequently met with. Apart from the ray-reduction these 

 spicules resemble the regular stauractines above described. When two of their 

 rays are reduced, these reduced rays may be either adjacent (Plate 15, fig. 21) 

 or opposite (Plate 15, fig. 5). A stauractine in which all the four rays are 

 reduced is represented (Plate 15, figs. 9, 10). This spicule is only 30 ix in diame- 

 ter, and has cylindrical, terminally rounded rays 8 n thick. 



Irregular stauractines with unequal interactine angles (Plate 16, fig. 12) or 

 with curved rays (Plate 15, fig. 11) are met with much more rarely. Apart 

 from the irregularities characteristic of them, they also resemble the regular 

 stauractines above described. 



Among the dermal spicules with less than four rays, which are doubtlessly 

 to be considered as stauractine-derivates with reduced ray-number, triactine and 

 diactine forms occur. Most of the triactine stauractine-derivates (Plate 15, 

 figs. 4, 6) are straight or curved rhabds, 83-125 m long, from the central part of 

 which arises a ray-rudiment 9-12 n long. Some of them, however, appear as 

 more or less regular triactines with rays nearly equally long, enclosing fairly 

 equal angles with their neighbours. The diactine stauractine-derivates are 

 straight, or slightly curved, or strongly angularly bent. The latter resemble 

 more or less widely open compasses. In regard to the thickness of their rays 



