



58 



THE SPONGES. 





specimens of F. occa, differing in some details from the pentacts present 

 in the specimen of F. occa which Schulze had from the Bay of Bengal 



(1895, p. 67). 



The uncinates, Fig. 11, Plate 6, commonly show a difference between 

 the two ends. At the external end, as over the middle part of the shaft, 

 the spines are pretty long and nearly parallel to the shaft. Toward the 

 inner (gastral) end they become minute sharp denticulations. The length 

 of the spines varies considerably on different uncinates, and they may 

 degenerate all over the spicule into denticulations. The uncinates may 

 even become smooth, in which case I have found them to be slenderer 

 than the common forms. A common size is about 600 /x long by 5 /x 

 thick, excluding the spines. But spicules up to twice this size occur. 



Oxyhexasters are abundant, and similar to those of the type (Schulze, 

 1887, Plate LXXI. Fig. 7). The principal ray is 20-24 /x long, and bears 

 3, 4, or 5 terminals, which are about half as long as the principal. Oxyhex- 

 asters occur here and there which differ from the common form in that 

 the terminals are as long, or nearly as long, as the principals. Such 

 spicules are somewhat larger than the common form, and usually there 

 are only two or three terminals to a principal. 



The dermal clavulae, Fig. 2, Plate 7, with rare exceptions, have smooth 

 ovoidal heads, and are about 300 //, long. The stalk is slender and 

 smooth, except near the point, where it is roughened. The spicules occur 

 in the usual position, in groups surrounding the proximal rays of the 

 pentacts. The number in a group is inconstant, always small (3-5); but 

 some spicules may have Mien out. The exceptional dermal clavulae, 

 which are very rare, are like the form common on the gastral surface. 



In the type (Schulze, 1887, p. 283) the shape of the upper end of the 

 dermal clavula varies from a many-toothed umbel, or a tuberculated 

 swelling, to a smooth club. The first-mentioned shape is the predominant 



form. 



The gastral clavulae are arranged, like the dermal, in small groups 

 of 3 to 5, round the proximal rays of the corresponding pentacts (Fig. 6, 

 Plate 7). The common form, Figs. 12, 13, 14, Plate 6, has an umbel 

 with 6-9 teeth, which overarches a smooth swelling. Umbels with as 

 many as 16 teeth occur, and occasionally a spicule is found in which the 

 swelling is minutely tuberculate. In the latter cases observed the umbel 

 had 14-16 teeth. The stalk is like that of the dermal clavula, but is 



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