110 THE VOYAGE OF H.M.S. CHALLENGER. 



siliceous webs whose threads are frequently provided with small terminal hooks or 

 umbels. I would venture to suggest that we have here to deal witli the retiforni 

 siliceous skeleton of certain Eadiolarians in which terminal hooks or pronged terminal 

 discs frequently occur quite similar to the hexasters of Hexactinellida. 



This form was found in the neighbourhood of Dominica, on muddy ground, and at a 

 depth of 6 1 1 fathoms. 



In spite of the characteristic floricome described by Oscar Schmidt, it must still 

 remain doubtful whether this form really belongs to the Euplectellidse. 



Genus 7. Hyalostyhis, n. gen. 

 This genus contains only one species, Hyalostyhis dives. 



Hyalostylus dives, n. sp. (PI. LXX). 



This Hexactinellid (PI. LXX. fig. 1) was dredged in the Mid South Pacific Ocean, 

 lat. 39° 41' S., long. 131° 23' W. (Station 289), from a red clay ground at a depth of 

 2550 fathoms. The soft loose body measures 5 '5 cm. in length, while from the lower 

 end there extends a much damaged awd-shaped stalk, 11 cm. long, and 2 to 1 mm. 

 thick. The whole sponge has been apparently so much compressed and distorted in the 

 dredge, that from its present state it is ditticult to decide certainly as to the original 

 form of the living organism, though a reconstruction is, to a certain extent, still 

 possible. In general form the body of the sponge resembles a laterally mucli-corapressed 

 cone, of which one of the narrow sides is uniformly rounded and the other much 

 folded. The broader upper end is not transversely, but obliquely truncated, as the 

 rounded, somewhat S-curved narrow side is rather longer than the other, which exhibits 

 a simple convex contour. The upper surface is contracted in funnel-like fashion, and 

 exhibits an irregularly folded infundibular opening. The lower end of the body is not 

 drawn to a point, but is slightly rounded. The stalk springs from the base of the 

 rounded, unfolded narrow side, and becomes gradually slender throughout its length. 



As the sponge w^as given to me for investigation in an undoubtedly much altered form 

 and condition, several questions as to its anatomical structure, and these of essential 

 importance in determining its systematic position, have unfortunately to be left un- 

 answered. Thus it must remain doubtful whether the cup-form of the body represents 

 the original shape, whether the smooth external surface is really dermal, whether the 

 folded portion of one side is merely a part of the external surface, whether the styliform 

 stalk represents the intact form or only a fraction of the original, and so on. 



Microscopic examination soon revealed that the tissue was not sufficiently well 

 preserved to admit of tlie recognition of the arrangement and structure of the chambers, 



