SPONGES. -HALLMANN . 



J 49 



more or less towards its extremity. Quite com- 

 monly the basal extremity of the spicule is either 

 abruptly or acuminately pointed, and the spicule ac- 

 cordingly sometimes passes into an asymmetrical 

 oxea. The length varies from 140 to 1701^ and the 

 maximum diameter is 4^. 



(ii.) The (accessory) acanthostyles are sub-conical, with 

 moderately large, irregularly scattered, recurved 

 spines. They are rarely less than 60 }i long and 

 attain a size of 96 x 8 p. 



Microscleres. — 



The chelae (isochelae arcuatae) vary from about 18 to 27 \i in 

 length ; except for a greater curvature of the shaft in the case 

 of the shorter spicules there is no appreciable difference in 

 form between the longest and the shortest. In their earliest 

 stage of development they appear as a slender, slightly curved 

 rod ; the alae are well advanced in development before the- 

 rudiment of the front palm makes its appearance. At a certain 

 stage of their growth many bear a rather close resemblance to 

 the longest of the three chelae shown in text-figure 52a for 

 Wilsonella oxyphila. 



Loc. — Coast of South Australia; (?) fifteen miles south of 

 St. Francis Island ("Endeavour.") 



Wilsonella oxyphila, sp. nov. 



(Plate xxxiv., fig. 3; and figs. 52, 52a.) 



Sponge flabellate, simple or proliferous. (?) Oscula 

 small, marginal. Surface even, or with faint radiating 

 grooves, or areolately pitted. Dermal membrane dis- 

 tinct, thin. . Main skeleton an irregular reticulation of 

 moderately slender, closely echinated fibres, with a 

 slender core of skeletal spicules. Interstitial spicides 

 scarce. Megascleres of both kinds {the accessory in 

 lesser number) are sparsely scattered in the dermal mem- 

 brane, together with frequent chelce. Megascleres : — 

 (i.) Skeletal smooth substyli, 200 x 3 ]i; {ii.) accessory 

 acanthostyli and {occasional) acanthoxea, 80 x 4.5 )i. 

 Microscleres : — Isochelce arcuatce, approaching the 

 palmate form, 16 to 26 ^^ long. 



Introductory Remarks. — There are two specimens which I 

 assign to this species. In their external appearance there is 

 nothing that would suggest a specific identity, but they agree 

 so perfectly in their spicular characters that one hesitates to 

 separate them even as different varieties. Accordingly I have 

 thought it best, whilst uniting them under a single name, to 



