34 HOLASCELLA TARAXACUM. 



its thickest point, which Ues only a very short distance below the end, the distal 

 ray is 16-60 ii thick. The proximal and the lateral rays are often curved; the 

 distal ray is straight. The proximal and lateral rays are smooth apart from their 

 ends, which are often slightly spined. The basal part of the distal ray is smooth, 

 or only slightly spined; its thickened end is covered with spines, situated very 

 oliliquely and directed upwards toward the tip of the ray. These spines are 

 quite numerous and close together, have a maximum length oi b ix, and are 

 about 4 n thick. They appear as oval protuberances, the ends of which are 

 drawn out to sharp and slender points. The tip of the ray is free from spines 

 for a distance of about 10 ti. In the distal rays of medium thickness the 

 tip appears as a broad cone, in the very thick ones as a broad round dome. 

 The proximal part of the axial thread of the distal ray is quite thin, its distal 

 part thickened, and about 1.5 ;u broad. 



I have observed a few spicules in the spicule-preparations which also appear 

 to be hypodermal or hypogastral hexactines, but which differ from the spicules 

 above described by one, two, or even three of their lateral rays being thickened 

 and spined like the distal ray. 



The smooth root-spicules are all broken off at the lower, distal end. The 

 longest fragments measured were 150-160 mm. long. Proximally these spicules 

 are gradually attenuated to a fine point. Their thickest portion is about 120 

 mm. from the proximal end; here they are 100-340 m thick. 



The spined, anchor-like root-spicules (Plate 22, figs. 26, 37; Plate 23, figs. 

 2, 3) are remarkably scarce. All those seen were broken so that I cannot give 

 their length. To all appearance they are much shorter than the smooth root- 

 spicules. Near their distal end these anchor-spicules are 12-17 ^ thick. The 

 end itself is thickened to a terminal tyle, 48-56 fi broad, 54-70 ^ long, and in 

 shape like a blunt, inverted cone with convex sides or a rotation-paraboloid. 

 From the shaft of the spicule and from the margin of the upper, basal face of the 

 terminal tyle arise conic, obliquely situated, backwardly directed spines 7-17 fj. 

 long. The axial cross (morphological centre) of the spicule lies in the terminal 

 tyle (Plate 23, figs. 2, 3). These spicules are not, like the similarly shaped 

 anchors of the species of Holascus, diactines, but monactine tylostyles. 



Among the micro-oxyhexactines, -oxypentactines, and -oxytetractines {staur- 

 actines) (Plate 22, figs. 20-25), the hexactine forms appear to be the most 

 abundant. The rays of these spicules enclose angles of 90° with their neighbours 

 and are equal in most of the hexactines and stauractines. In the pentactines 

 and some of the hexactines (Plate 22, figs. 20, 21) a differentiation of the three 



