SP0N6IIBA. 471 



of that form, in its inorusting habit (^purpurea beiag massive), in 

 the inferior diameter of the shaft of the spinulate and the superior 

 length of the spinispirular spicule (in pv/rpurea these dimensions 

 are respectively "013 and "016 millim.), the latter usually consisting 

 in purpurea of only one to one and a half bends. 



The single spirit-specimen measures 32 millim. (1^ inch) in 

 height by 30 millim. in longest diameter, by 10 mUlim. (^ inch) 

 in greatest thickness. 



TETRA CTINELLIDA. 



The family Lithistidm is not represented. This is not surprising 

 if it is remembered that the depths investigated did not exceed 40 

 fms. Mr. Carter's better fortune with coUeotions from Ceylon is in 

 part due to the greater depth at which the specimens were obtained. 



CHOEISTID^. 



Sollas, Am. 8f Mag. N. H. 1882, ix. p. 164. 



Prof. Sollas has since proposed a different arrangement of the 

 TetractineUida, but the division into Choristidse and Lithistidae 

 appears a natural and convenient one. Tlie species obtained, 

 though few in number, are of remarkable interest, and aU new to 

 the Australian seas. 



STELLETTA, Schmidt. 



This genus, as at present constituted, is decidedly heterogeneous. 

 Some of Schmidt's and Carter's species appear referable either to 

 Geodia, or some genus intermediate between Qeodia and Stelletta 

 (by virtue of the transitional character of their baU-steUate spicule), 

 while S. euastrum appears distinct by virtue of its disJcs. The more 

 typical forms appear to be divisible into subgroups which coincide 

 roughly with their geographical distribution. Thus the Atlantic 

 species mostly have medium-sized stellates, with numerous rather 

 coarse, pointed rays ; the Indo-Paoiflc ones have few-rayed stellates, 

 usually minute ; of the latter, the Fijian and two of the Ceylon 

 forms agree in having a small surface bacUlate or acerate spicule, 

 while one Ceylon form {S. teihyopsis) and all the Australian ones 

 known at present agree in having only minute delicate rayed' 

 stellates. 



The Indo-Pacific species of Stelletta, s. str., may be divided into 

 two groups ; — 



Group 1. With bacUlar or acerate flesh-spicule. 



1. S. (Ecionemia) acervus, Bowerbank, P. Z. S. 1873, p. 322, 

 pi. XXX. figs. 1-6. Fiji Islands. 



. 2. S. (Ecionemia) densa, id. I. e. p. 322, pi. xxx. figs. 7-14. Fiji 

 Islands. 



3. S. (Tisiphonia) 'nana. Carter, Ann. & Mag. N. H. 1880, v. 

 p. 138, pi. vii. fig. 43. Gulf of Manaar, Ceylon. 



