297 



in diameter; the microdiscohexasters however do not attain the very 

 kirge size (70/<) of some of those found in the Belgica specimens. 



Five specimens, which are placed in a new subspecies minuta have 

 not only smaller microdiscohexasters, but smaller calycocomes, varying 

 from 160—250 a in diameter. Three s^^ecimens of this species have no 

 calycocomes, and are placed provisionally under the new subspecies. 



A velum is present in all the specimens: i. e. a certain number of 

 hypodermal pentactius project at different levels beyond the surface. 



The species Rossella liexactiìiophila Kirkp. (Discovery Report. 

 Hexactinellida p. 12) is found to be a subspecies of 7?. racovitxae Topsent. 

 viz subsp. hexactinophila. It was supposed to differ from i?. racovitxae 

 racovitxae on account of the presence of a velum in the former^ but this 

 structure is now found to exist in H. racovitxae. 



Localities. Specimens were obtained from Gauss Station, from 

 depths of 380-385 m. 



Rossella gaussi n. sp. 



There are four specimens of this species. The largest example is 

 globose, being 3,9 cm high, and 3,6 cm broad. The surface is covered 

 with rounded wart-like hummocks. There is a usually well developed 

 velum of hypodermal pentactins with mostly cruciate tangentials with 

 densely granular surface. 



The prostalia pleuralia are strong, thick sharp-pointed diactins. 



The parenchymal diactins have rounded ends. The autodermal 

 pentactins have a granular surface. The character that at once becomes 

 obvious on examining sections is the great abundance of discohexasters 

 and the almost total absence of oxyhexasters. 



These are the features which distinguish the new species from the 

 nearly related R. racovitxae. The diactine principalia, the auto-dermalia 

 and auto-gastralia are nearly similar in both species. 



The calycocomes, which in the type specimen are more abundant 

 in the dermatosom than in the gastrosom, vary in size, the largest being 

 312 u in diameter. In the type specimen heterodiscohexactins (F. E. 

 Sch.) seu monodiscohexaters (Kirkp." are very common, but hemidisco- 

 hexasters are more frec[uently found in the other three specimens. In the 

 type, the heterodiscohexactins (F. E. Sch.) seu monodiscohexasters 

 Kirkp.' seem to replace to a great extent both calycocomes and micro- 

 discohexasters in the gastrosom. The specimen named it', racovitxae 

 in the Discovery Report Hexactinellida p. 14, belongs to this species. 

 At the same time, it has no velum, and the tufts of pleuralia emerge 

 from pointed conules: but the discohexasters are abundant, and the 

 oxyhexasters almost absent. 



Localitv. Gauss Station 350 — 380 metres. 



