sroxGiiDA. 421 



55. Rhizochalina singaporensis, Carter, var. ( Plate XLI. fig. s.) 



Phlceodictyon Bingaporense, Carter, Ann. ty Mag. N. II. ( L883) xii. 

 p. 320, pi. \iii. t i lt . 17. 



With this species I identify a series of specimens which usually 

 have the outward habit of K.fistulosa, but in winch a large pro- 

 portion of the (usually acerate) spicules have both cuds moreor less 

 rounded. In the most perfecl specimen the cortex is glabrous, 

 chestnut to purplish-brown in colour, thin; the fistula- are wanting 

 on one, presumably the lower, surface. A smaller specimen consists 

 of a barrel-shaped mass adherenl by its lower surface to two other 

 sponges, and giving off from one lateral extremity one, from the 

 other two fistulas and no others. A detached fistula exhibits 

 furcation, dividing into two unequal branches at an angle of about 

 30° to each other. In one remarkable specimen the central part of 

 the body is elongate, slightly compressed, and measures llOmillim. 

 (4^ inches) in its present length, while its diameter does not exceed 

 12 millim. anywhere ; in its other characters it agrees well with 

 the above specimens. A fragment of the bulbous part of a large 

 specimen shows that part of this specimen, when perfect, to have 

 possessed a diameter of about 75 millim. (3 inches). 



The ends of the spicules show almost every stage between a 

 merely blunted point and a rounded end like that of the base of an 

 ordinary acuate spicule : some thin, completely acerate forms, which 

 occur mixed with the blunt forms in the subcortical tissues, are 

 perhaps the young of the latter, indicating the typical shape from 

 which the adult spicules have diverged. The largest adult spicules 

 have nearly the same size as the acerates of the typical form of 

 It. fistulosa, viz. -3 by "0127 millim., but they vary immensely in 

 length; the thin acerates measure "28 by "004 millim. In Carter's 

 specimen the acerates measure - 3 by '017, the blunt forms '04— "08 

 by -004 millim. 



Three fistula? retain their ends, and these are finger-like and 

 closed. 



Hab. Prince of Wales Channel, West and Alert Islands, Torres 

 Straits, 7 fms. 



Distribution. Singapore (Carter). 



I may explain that I had at first distinguished this form as a 

 variety of R. fistulosa ; but as Mr. Carter has, since then, published 

 a description of it as a distinct species, and as T had already felt 

 that it should perhaps be so described, I assign the name proposed 

 by him to the Australian specimens. 



56. Rhizochalina spathulifera. 

 (Plate XXXIX. fig. E ; Plate XLI. fig. q.) 



Main body elongated, flexuous, cylindrical or somewhat compressed, 

 12-17 millim. in greatest diameter. External portion (cortex) in dry 

 state even, hard and dense on the stem, where it is about '7 millim. 

 thick; rather uneven, porous and compressible on the brandies; 



