HYALONEMA (PRIONEMA) AGUJANUM. 



263 



shaft (Plate 74, fig. 3; Plate 77, figs. 2, 3). The end-part.s of the teeth are often 

 bent rather abruptly inward and they generally converge. The teeth have the 

 usual T-shaped transverse section. Their outer and upper band-shaped part 

 is, in the larger serrated amphidiscs, nearly uniformly (18-22 m) broad throughout, 

 attenuated only slightly distally, and rounded at the end. The lateral and termi- 

 nal margins of the teeth are bent down shaftwards and serrated. The serration- 

 teeth are triangular, sharp-pointed, and usually directed more or less backwards. 

 The lateral ones are 1.5-2 m long and 1-2 ^ broad, the terminal ones smaller. 



In var. tenuis, form ^, and in var. lata the serrated amphidiscs attain a larger 

 size than in var. tenuis, form B; and in var. lata the average relative breadth of 

 the anchors is considerably greater than in the two forms of var. tenuis. The 

 dimensions of the serrated amphidiscs are : — 



SERRATED AMPHIDISCS. 



• When there are two or more numbers in this zone it indicates that the length frequency-curve 

 pertaining to the spicules of the variety or form has more pronounced elevations than one; in these the 

 serrated amphidiscs do not appear to be biometrically homogeneous groups. 



