398 Mr. H. J. Carter on 



thinness ; here and there stouter, when the usual sexradiate 

 central inflation, which is characteristic of the hexactinellid 

 spicule, may be detected on them (fig. 4, e) ; fine form about 

 50 by -i--1800ths in. in its greatest dimensions (fig. 4, f) ; 

 stouter form about 60 by l-1800ths in. (fig. 4, e). 4, scopuli- 

 form spicule or scopula consisting of a smooth shaft, attenu- 

 ated and sharp-pointed at the free end, furnished at the other 

 with 2, 3, or 4 (usually 2 in this specimen) slightly divergent 

 rays, diminishing in size outwards, but ending abruptly, that 

 is without terminal inflation or head, thickly microspined 

 throughout; spines towards the free ends recurved; total length 

 of spicule 33-1800ths in.; rayabout5-1800ths in. long, but both 

 very variable in this respect (figs. 4, c, and 5) . o, rosette, sex- 

 radiate, arms smooth, straight, radiating at equal angles from 

 the centre, without inflation of the latter, terminating in five 

 rays more or less, which are long, divergent, and pointed for the 

 most part, but sometimes capitate (fig. 6, «), or more or less 

 numerous and always capitate, arranged floral ly (fig. 6, b), the 

 former accompanied by short and the latter by longer arms ; 

 or in a small variety the arms may be thick and elongated 

 into a point without rays, but with four or more compara- 

 tively long spines on each arm, outwardly directed ; size about 

 20-1800ths in. in diameter (fig. 7). 6, internal or skeletal 

 sexradiate, much the same as the dermal form, but with all 

 the arms equally developed ; very variable in size (fig. 4, b, 

 and fig. 10). 7, skeletal fibre, microspined, irregularly sex- 

 radiate, chiefly built on the foregoing spicule (fig. 4, a) . No. 1 

 is for the most part confined to the dermis, where the arms, 

 overlapping those of the neighbours, give rise to a quadrilateral 

 reticulation, whose areas are frequently again divided into 

 four triangular spaces by a sexradiate of the same kind 

 situated in the centre (fig. 9) ; interstices throughout tym- 

 panized by the dermal sarcode in which the pores are situated. 

 No. 2, the barbula, is scarce. No. 3 (fig. 4, /) in bundles, 

 characteristically plentiful, especially in the dermal struc- 

 ture in its finer form, while the stouter one is chiefly found in 

 the interior with nos. 4 and 5 (the scopula and the rosette), 

 intermingled with the skeletal fibre, which is chiefly built on 

 nos. 1 , 3, and 6. Size of specimen given at the commence- 

 ment. 



Bab. Marine. 



Loc. Japan, Misaki, at the entrance of the Bay of Tokio 

 (Yedo). 



Obs. This is an instance in which not only the general 

 form but the internal structure so closely resembles PkakelUa 

 ventilabrum, Bk. (Mon. Brit. Spong. vol. iii. pi. xxii.), that, but 



