42 HOLASCELLA ANCORATA. 



in total diameter. They generally have only one, sometimes two, very rarely 

 three end-rays. Most of them are microdiscohexactines with one end-ray on 

 each main-ray ; some hemidiscohexactines with one end-ray on some main-rays 

 and with two end-rays on others. A few are true discohexasters with two end- 

 rays on all or with two end-rays on some and three end-rays on the other main- 

 rays. The main-rays are regularly arranged and, in the same spicule, fairly 

 equal. They are smooth, about 5 n long and 2.5-3.7 n thick. The end-rays are 

 straight or slightly irregularly curved, 50-110 yu long, thinnest some distance 

 below the distal extremity, and thickened at both ends. The proximal end is 

 2-3 M thick, the thinnest point 0.7-1.5 n, and the distal end 2.6-4 fi. The end- 

 rays bear very minute spines on their sides and a verticil of large, anchor-teeth 

 like, strongly recurved spines at their end. These terminal spines are conic, 

 8-10 M. long and 1.2-1.6 n thick at the base. They are not joined at the base 

 to a terminal tyle or disc, and together form an exquisite anchor, 9-12 n broad 

 and about as high. When two or three end-rays arise from a main-ray, they are 

 usually arranged somewhat irregularly and enclose angles of 20°-45° with the 

 continuation of the main-ray. When, as is the rule, there is only a single end- 

 ray, it lies in the continuation of the main-ray, and usually passes into it so 

 gradually that main- and end-ray together appear as a simple hexactine ray. 

 Such simple rays are 65-115 ti long. 



Axial threads are found only in the main-rays. They appear as thin, fairly 

 straight rods, are about 5 m long, and terminate abruptly at the point where the 

 main-ray divides into the two or three end-rays (Plate 23, fig. 7, right), or passes 

 into the single end-ray (Plate 23, figs. 6, 7, left, upper and lower). The simple 

 rays with only one end-ray consequently possess an axial thread only in their 

 basal (main-ray) part. 



The few main-ray crosses observed, which may be centres of graphiocomes , 

 consist of regularly arranged, equal, straight main-rays 10 m long and 3.5 n thick, 

 from the ends of which large numbers of end-rays arise. 



The floricomes (Plate 24, figs. 4-7) measure 48-60 m in total diameter. 

 Their main-rays are regularly arranged, in the same spicule equal, cylindrical, 

 straight, 6-7 yu long, and about 1.5 ^ thick. Each main-ray bears a verticil of 

 about twelve end-rays. All the end-rays arise at exactly the same level, 1-1.5 ^ 

 below the distal end of the main-ray, which protrudes for that distance in the 

 shape of a rounded knob beyond the ring-shaped line of their insertion. The 

 end-rays of the same verticil are exactly equal in size, shape, and position, rela- 

 tive to the main-ray from which they arise. They are, measured along their 



