300 



Aulorossella Kirkp. 



1908. Aulorossella Kirkpatrick Discovery Hexactinellida p. 14. 



The genus was established to include 3 species of Antarctic Rob- 

 sellinae, and was characterised by having 3 kinds of discohexasters^ and 

 oxypentactine hypodermalia with short prong-like rays making an acute 

 angle with the shaft. Accordingly the dermal surface is not supported 

 by the tangential rays of pentactine hypodermalia and there is no velum; 

 a root-tuft is usually present, but never marginalia. The Gauss col- 

 lection includes several examples of a new species and subspecies of 

 Aulorossella. In the typical form the hypodermal pentactins and the 

 tufts of diactine pleuralia have disappeared entirely; in the variety 

 both kinds of spicules still persist. Accordingly the generic definition 

 must be slightly emended as follows: ''Rossellinae . . .« with or without 

 hypodermal pentactins, these spicules when present having short smooth 

 pronglike tangential rays making an acute angle with the radial ray. 



Aulorossella vanhoeffeni n. sp. 



Description. The single specimen is in the form of an oval barrel- 

 shaped thick walled sack with a well developed root-tuft. The body is 

 11 cm long, and 5,6 cm in diameter about the middle, and with a cir- 

 cular oscule 2,2 cm in diameter; the wall attains a thickness of 12 mm; 

 the basalia all end in four-pronged anchors. The colour is grayish buff 

 in alcohol. The greater part of the surface is uniformly smooth , and 

 entirely devoid of pleuralia, but at the lower end are conical tubercles 

 whence tufts of basalia emerge. Beneath the dermal surface is a net- 

 work of bundles of hypodermal diactins, the meshes of which network 

 are spanned over by the tangential rays of the autodermal pentactins. 

 The gastral surface has a rough j)orous aspect. 



A marked feature is the size of the hypogastral spaces supported 

 by vertical bundles of diactine accessoria. 



Spicules. The diactine principalia are slender flexible sharp-pointed 

 diactins; very large isolated diactins occur also. The auto-dermalia have 

 a thickly spined surface — a characteristic feature in Aulorossella 

 generally. 



The auto-gastralia are hexactins with thickly -spined blunt-ended 

 rays. The calycocomes show a considerable range of variation, some 

 having simple perianth-like end rays without capitulum, others having 

 a central boss surrounded by end rays, and others again having a well- 

 marked cai)itulum. The total diameter varies from 140 — 190 /». The 

 mesodiscohexasters, 106 /< in diameter have short primary rays 6 // 

 long, and 2, 3, or 4 end rays. Microdiscohexasters 47 // in diameter. 



