HYALONEMA (HYALONEMA) TENUIFUSUM. 223 



macramphidiscs, small macramphidiscs, and micramphidiscs. The large macr- 

 amphidiscs are rather rare, the minute tylostyles, which may be foreign, very 

 scarce. All the other kinds of microscleres are abundant. At the point of 

 emergence of the stalk, numerous monactine to hexactine, stout acanthophores, 

 occur at the base of specimen (a). The stalk itself consists of a dozen stout, 

 and a number of more slender spicules twisted in the usual way. 



The dermal pinules (Plate 68, figs. 18-21, 24, 25) are nearly always pentac- 

 tine, very rarely hexactine. The distal ray is straight, 33G-550 yu long, generally 

 430-530 ju, and, at the base, 8-11 /x thick, rarely as much as 13 /x. Its proximal 

 end is smooth; for the rest of its length it is covered with upwardly directed spines 

 which are sparse, stout, short, straight, or only slightly curved, and strongly 

 divergent below, and which increase in density and length, and decrease in 

 divergence and thickness above, up to a point a short distance below the tip of 

 the ray. From this point onward to the end of the ray the spines again become 

 smaller, less divergent, and more and more curved, concave to the ray, the 

 distal parts of the uppermost spines being nearly parallel or even convergent. 

 The maximum thickness of the distal ray, together with the spines, is 37-05 yu. 

 The point of maximum thickness lies high up. The proportion of the total length 

 of the distal ray to the distance of the point of maximum thickness from the 

 centre of the spicule (the proximal end of the distal ray) is, in the dermal pinules 

 of specimen (a), 100 : 64 to 84, on an average 100 : 79, in the dermal pinules of 

 (6) 100 : 67 to 84, on an average 100 : 75.2. Wlien the point of maximum thick- 

 ness is very high up, the distal ray, together with the spines, appears club-shaped. 



The lateral rays of the same spicule are usually fairly equal, straight, cylin- 

 droconical in the basal and middle-parts, and abruptly pointed at the end. 

 They are, in the dermal pinules of specimen (a) rather smooth, and 52-90 /x 

 long; in those of (6) spiny, and 40-75 m long. The rare hexactine dermal pinules 

 are quite similar to the pentactine. Their proximal ray reaches 103 n in length. 

 In a good many pentactine pinules of specimen (b) a little cluster of spines, 

 about 4 fx long, arises from the centre of the proximal face of the cross formed by 

 the lateral rays. This central spine-cluster may be a remnant of a reduced 

 proximal ray. 



The gastral pinules (Plate 68, figs. 2, 3) are, like the dermal, usually pentac- 

 tine, rarely hexactine. The distal ray is 101-228 m long, and 4-10 fx thick at the 

 base. It bears sparse spines directed obliquely outward and upward. The 

 spines are usually only slightly curved, concave to the ray. Occasionally, 

 however, the lowest spines exhibit a strong curvature in this direction. The 



