BATHYDORUS LAEVIS SPINOSISSIMUS. 
99 
its full size. The partly and wholly smooth pentactines, above referred to, 
should, I think, therefore be considered as not completely developed, adolescent 
spicules, in which the spines are not yet, or as yet only partly, formed. 
The rays of the rare apparently pentactine-derivative hexactines (Plate 16 , 
fig. 3) are 12-25 n thick at the base. One of them is elongated and 570 /x-2 mm. 
long. This ray corresponds with and is similar to the proximal ray of the pentac- 
tines above described. The four rays vertical to this elongated ray are, in the 
same spicule, more or less unequal in length, the longest being 160-500 n long, 
the shortest 135-225 They correspond with and are similar to the lateral 
rays of the pentactines. The sixth ray, which lies in the continuation of the axis 
of the elongated one, is straight, conic, blunt, and 88-420 /x long. 
The pentactines with relatively short lateral rays (Plate 16 , figs. 1, 2) have an 
apical (probably proximal) ray 780 /x-2. 7 mm. long and 13-22 /x thick at the base. 
This ray is generally more or less curved. It is nearly cylindrical in its proximal 
part and gradually attenuated to a blunt end. The lateral rays of the same 
spicule usually differ in length, the longest being 200-290 /x, the shortest 145- 
221 fx long. They are at the base about as thick as the proximal ray, cylindrical, 
and blunt. The rounded end is usually one to two thirds as thick as the base of 
the ray. The lateral rays enclose angles of considerably less than 90° with the 
apical (probably proximal) ray, and are usually curved, concave to the latter. 
The lateral rays of these pentactines exhibit the same spinulation as the pentac- 
tines with long lateral rays described above. The proximal ray is less spiny, 
sometimes apparently quite smooth. 
The rare regular hexactines with fairly equal rays measure 0.6-2 mm. in 
diameter and have mostly smooth, rather straight, cylindroconic, terminally 
rounded rays 0.35-1.1 mm. long and 15-40 /x thick at the base. 
Besides these regular ones I have found a few irregular hexactines, one of 
which is represented on Plate 16 , fig. 18. This spicule has rays 250-830 /x long. 
The dermal spicules are di- to hexact.ine, by far the greater number of them 
being tetractine (stauractine). Most of these stauractines are fairly regular, 
having four properly developed, straight rays differing only slightly in length 
and enclosing equal angles with their neighbours. Besides these a few staurac- 
tines occur in which either one, two, three, or all four rays are greatly reduced 
in length, or one or more rays are strongly bent, or the angles between the rays 
are unequal. 
The regular stauractines (Plate 14 , fig. 11; Plate 15 , figs. 1, 2, 19; Plate 16 , 
figs. 13, 14) generally measure 80-215 /x in diameter. In specimen A, I have 
