HYALONEMA (OONEMA) BIAxVCHORATUM PINULINA. 



325 



inner contour (the inner margin of the keel) and the lateral margin, on the 

 other hand, diverge from the shaft. 



In specimen a I found a remarkable abnormal small macramphidisc (Plate 

 85, fig. 8) 190 At long, with terminal anchors respectively 80 and 100 ^ long and 

 about 100 /Li broad. In this spicule each anchor is composed of two partly 

 incomplete and somewhat irregular verticils of anchor-teeth, instead of a regu- 

 lar single one. This duplication is much more pronounced in one (the upper one 

 in the figure) than in the other terminal anchor. Some of the teeth belonging 

 to the inner (supernumerary) verticils are nearly straight, extend obliquely 

 backwards, and are widened at the end to irregularly oval terminal discs. The 

 position of these terminal discs is such that if the whole amphidiscs were assumed 

 to be enclosed in a tight-fitting ovoid mantle or shell, the outer faces of the 

 terminal discs would come to he exactly in the (inner) surface of such mantle 

 or shell. This observation seems to me to be of sinular import as the one on 

 an abnormal amphidisc found in Hyalonema (Prionema) agujanum var. tenuis 

 (p. 262, Plate 75, figs. 35-37); both favor the view that each amphidisc is 

 formed within a single ovoid cell. 



The chief dimensions of the large micramphidiscs are : — 



In these amphidiscs the shaft is straight. The central tyle is not defined 

 and passes gradually into the adjacent part of the shaft. Tyle and shaft are 

 very spiny. 



