SPONGES. 77 



pointed or even strongylote, a condition to which there is only a tendency in our 

 specimen. Our species is also very closely related to Pilochrota pachydermata, 

 Sollas, from Tahiti, hut differs in certain respects, such as the form of the chiaster, 

 which is not tylote in /'. pachydermata. 



R.N. 176 (collected in the lagoon inside the reef, Galle, shallow water, by 

 Mr. Hoknell, after whom, on Professor Herdman's suggestion, 1 have much pleasure 

 in naming the species). 



Stelletta, Schmidt. 



Microscleres euasters of two forms. 



It might be advisable to sub-divide this genus according to whether or not a 

 fibrous cortex is present, as Sollas has done in similar cases. Stelletta herdmani 

 would then come under the first sub-division and S. vestigium under the second. I 

 do not, however, think it would lie desirable to take such a step until we know more 

 about the value of this character in classification. 



Stelletta herdmani, n. sp. Plate II., fig, 6. 



Sponge quite irregular in shape ; sometimes vallate ; sometimes with occasional 

 digitiform or mammiform projections ; often very much mixed up with coarse 

 calcareous debris. Surface uneven, very harsh to the touch and striate owing to the 

 presence of the huge megascleres immediately beneath the thin dermal membrane ; 

 not hispid except where apparently worn. Vents few, scattered on prominent parts, 

 up to about 3 millims. in maximum diameter ; leading out of deep cloacal tubes, 

 which are of about the same diameter and lined by a sieve-membrane. Inhalant pores 

 scattered in the dermal membrane. Colour (external) ranging from pale yellowish to 

 slate-grey in the same specimen The largest specimen is about 55 millims. in 

 greatest diameter, but is a good deal damaged and much mixed up with foreign 

 matter. 



Skeleton very dense and more or less confused ; consisting of irregular bundles of 

 huge oxea and trisenes, for the most part radiating towards the surface, but lying 

 tangentially beneath the dermal membrane and thus forming an ill-defined but dense 

 spicular cortex about 0'3G millim. thick. 



Spicules. (1.) Plagio- or protrieenes (Plate II., fig. G, a, b, c.) ; with short, stumpy, 

 conical cladi projecting more or less forwards, and stout shaft, usually somewhat 

 curved, more or less swollen at some distance below the cladi and tapering gradually 

 to a sharp point at the other end. Size somewhat variable, shaft up to about 

 1/2 millims. by 0"074 millim., with cladi - 18 millim. long. 



(2.) Oxea (Plate II., fig. 6, </.); fusiform, straight or slightly curved, tapering 

 gradually to a sharp point at each end; size about 2"8 millims. by 0"09 millim. 



(3.) Chiasters (Plate II., fig. G, e-h) ; very abundant in the dermal membrane, 



