250 PRIONEMA. 



defined central thickening can usually be made out. This is 1.2-1.9 m in trans- 

 verse diameter, that is 0.2-0.5 /i more than the adjacent parts of the shaft. 



The anchors are 5-11 y. long, one third to two fifths of the whole spicule, and 

 5.5-10 M broad. The proportion of their length to their breadth is 100 to 77-129, 

 on an average 100 : 107. The curvature of the anchor-teeth decreases distally, 

 and their end-parts are usually fairly straight. The total curvature is such that 

 the end-parts of the teeth are either parallel or slightly divergent. 



Besides the amjihidiscs above described, I found an abnormal amphidisc 

 with very unequal terminal anchors. This spicule is 42 /i long and has a shaft 

 2 M thick. One of its anchors measures 18 n in length and 13 n in breadth, the 

 other is 8 M long and broad. One half of this spicule appears as a mesamphidisc, 

 the other half as a micramphidisc. 



Of the species of Hyalonema hitherto described H. divergens F. E. Schulze ^ 

 appears to be the one most closely allied to the sponge above described. From 

 this it differs, however, to a considerable extent by the shape and dimensions of 

 the spicules. The large macramphidiscs 500 m long with ovoid anchors, which 

 are present in H. divergens, are absent in H. (H.) campanula. The macramphi- 

 discs with campanulate anchors are small and have a strongly spined shaft and 

 pointed anchor-teeth in H. divergens, and are twice as large and have, apart 

 from the centrum, a nearly smooth shaft and terminally rounded anchor-teeth 

 in H. (H.) campanula. These and the other less conspicuous differences are, 

 of course, quite sufficient for specific distinction. 



PRIONEMA, subgen. nov. 



Species of Hyalonema of which the amphidiscs of one kind have anchor-teeth 

 with serrated margin. 



The collection contains twenty-one more or less complete specimens and one 

 fragment of this subgenus. They belong to six species, all of which are new. 



' F. E. Schulze. Rept. Voy. ChaUenger, 1887, 21, p. 199, pi. 28, figs. 1-11. 



