Marine Sponges from Japan. 389 



(fig. l,bb), thus supporting the sarcode or soft parts and its 

 spicular contents, both externally and internally, that is on 

 each side of the skeletal wall. Spiniferous process or 

 spur about 15 to 25-lS00ths in. long by I to 2-1800ths in. 

 thick at the base; spines small, short, and broad, absent to- 

 wards the fixed end. Interstices or mesh work generally pre- 

 senting a tolerably regular aspect, but often just the opposite. 

 Loose spicules of five forms, viz. : — (1) Sexradiate (dermal), 

 with outer ray aborted or reduced to a mere globular tubercle, 

 often surmounted by a single spine in the advanced form ; 

 shaft or internal ray straight and the four arms spread out 

 horizontally, each somewhat curved towards the shaft, and all 

 more or less inflated and abruptly pointed at the extremity ; 

 some plentifully and generally microsp'med (fig. 4, a), and 

 others sparsely macrospined (fig. 4, b) , the latter chiefly on 

 the outer aspect; arms about 15-1800ths in. long, shaft about 

 the same length, but all the rays varying a little in this re- 

 spect, even in the same specimen, as well as the total size of 

 the spicule itself. (The raacrospined seems to be merely a 

 sequence or advanced state of the microspined form.) (2) 

 Acerate, straight, unsymmetrically fusiform, that is the outer 

 or projecting part being thicker than the inner two thirds of 

 the spicule, which is thus rendered long and whip-like j 

 sharp-pointed at each end, spined at short intervals through- 

 out, the spines long, smooth, and slender, respectively sup- 

 ported on bracket-like processes, which, being spirally arranged 

 around the shaft, give it an irregular zigzag appearance, all 

 sloping in the same direction, that is backwards or towards 

 the sponge, at a very slight angle upon the shaft, whose outer 

 or thickened end is extremely sharp, about 171-1800thsin. by 

 2-1800ths in. in its greatest dimensions, but very variable in 

 this respect ; longest spines, which are situated on the thickest 

 part of the shaft, about 2-1800ths in. As this spicule neces- 

 sitates a long description, and is common to almost all the 

 Hexactinellida, I shall hereafter allude to it under the name 

 of "barbula" (fig. 3 and fig. 8j. (3) Nail-shaped, consisting 

 of a long straight shaft/ which is slightly inflated and pointed 

 at the free end and expanded horizontally at the other into a 

 circular head more or less spined at the circumference ; shaft 

 microspined, especially about the free end, which is slightly 

 inflated and pointed, averaging in total length about 20 

 ISOOths in. ; head about l^-1800ths in. horizontally (figs. 5, 5, 

 and l,f). This spicule is so very abundant and presents 

 itself under so many different forms, that it might be as well 

 to enumerate them serially thus : — (rig. 7, a) that in which 

 the head consists of a simple, smooth, elongated, ovular, 

 Ann. & Mag. N. Hist. Ser. 5. Vol. xv. 27 



