HYALONEMA (PRIONEMA) PINXLIFUSUM. 289 



1.1 times longer than the next smallest. This point lies between 62 and 84 fi. 

 The amphidiscs 62 fi long and shorter, that is those 15-62 m in length, I consider 

 as micramphidiscs. Some of these micramphidiscs have relatively longer, others 

 relatively shorter anchors. The relatively long-anchored are 15-35 m long, the 

 relatively short-anchored 33.5-62 fx. The length frequency-curve of the micram- 

 phidiscs exhibits two marked principal elevations which correspond respectively 

 to the most frequent sizes of the long- and short-anchored forms. Within the 

 micramphidiscs two groups can therefore be distinguished, both from a mor- 

 phological and biometrical point of view: — smaller long-anchored micramphi- 

 discs, and larger short-anchored rnicramphidiscs. 



Of the amphidiscs 84 /j long and longer, that is those 84-470 m in length, 

 some have slender, others broad anchors. The slender-anchored are 84-380 n 

 long, the broad-anchored 370-470 n. The part of the length frequency-curve 

 pertaining to these amphidiscs exhibits one pronounced main elevation situated 

 at about 425 fi, close to its maximum end. The amphidiscs represented by this 

 main ele\'ation are all broad-anchored. These spicules form a homogeneous 

 group, which I name macramphidisc because it comprises the largest amphidiscs 

 of the whole series. Some of the slender-anchored amphidiscs have smooth, 

 others serrated teeth. Those with smooth teeth are 84-292 tx long, those with 

 serrated teeth 214-380 fi. Since the slender-anchored amphidiscs with serrated 

 teeth are on the whole much larger than those with smooth teeth; since all the 

 slender-rayed amphidiscs over 292 fi in length are serrated ones; and since the 

 morphological difference of teeth serrated and teeth smooth is of considerable 

 importance, I propose to consider these two kinds of slender-anchored amphidiscs 

 as belonging to two distinct groups; although biometrically, judged merely by 

 the length frequency-curve of the amphidiscs in general, they are not differen- 

 tiated. I name these two groups, which are, in size, intermediate between the 

 micramphidiscs and the macramphidiscs, smooth mesamphidiscs and serrated 

 mesamphidiscs respectively. The length frequency-curve of each exhibits, 

 when taken by itself, a depression, particularly well-marked in the case of the 

 curve of the latter. In the curve of the smooth mesamphidiscs this depression 

 lies at 121 ju, in the curve of the serrated mesamphidiscs at 260 m- As shown 

 by the two depressions of these two curves, a large and a small kind of spicule 

 can be distinguished in both of them. 



The amphidiscs of Hyalonema (Prionema) pinulijusum can accordingly be 

 arranged in seven groups : — • 



