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-derivaiive hexactines (Plate 16, 

 fig. 3) are 12-25 n thick at the base. One of them is elongated and 570 n-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 ^u long, 

 the shortest 135-225 m- 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 n long. 



The pentactines with relatively short lateral rays (Plate 16, iigs. 1, 2) have an 

 apical (probably proximal) ray 780 ^-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 n, the shortest 145- 

 221 n 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 saine 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, terminallj' 

 rounded rays 0.35-1.1 mm. long and 15-40 n 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 m long. 



The dermal spicules are di- to hexactine, 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 m in diameter. In specimen A, I have 



