370 Mr. H. J. Carter on 



goiial or honeycomb appearance on the surface. In S. crihro- 

 crusta it consists of a thick incrustation of foreign material, 

 which externally presents a polygonal lattice-like reticulation 

 in slight relief, whose interstices in the perfect condition are 

 diaphragmed with sieve-like pore- structure, which, in the 

 worn state, is replaced by a single circular hole ; while inter- 

 nally this crust is attached to the circumferential portion of 

 the subjacent fibrous skeleton by a few straight, single, deli- 

 cate filaments, which for the most part do not penetrate the 

 crust sutficiently to appear on the surface ; indeed, so slight is 

 this attachment that on desiccation the crust cracks up, through 

 partial collapse of the sarcodic interior, and thus separates 

 itself from the filaments of the subjacent fibre. 



In Stelosjyonffus kevi's the abundance of keratose skeletal 

 fibre enables it under desiccation to retain its original form, 

 while in 8. crihrocrusta there is more or less corrugation and 

 breaking-up of the crust, owing, as just stated, to the shrink- 

 ing of the sarcode internally. 



Thus the keratose fibro-skeletal structure of S. crihro- 

 crusta is so delicate and so scanty that it could hardly sustain 

 the wash of the sea-shore waves without going to pieces, 

 while that of S. Icevis is so firm and dense that the utmost 

 washing of the waves could hardly destroy its structure ; hence 

 thelatter has been found in great numbers on the South-Austra- 

 lian shores, as our museums and private collections testify ; 

 while I have never seen a specimen of 8. crihrocrusta except in 

 Mr. Wilson's collection, where the specimens were transferred 

 from the dredge directly to a vessel containing methylated 

 spirit and water for preservation. 



The spirit-preserved specimen described and illustrated by 

 Bowerbank under the name of " Halispongia choanoides^'' so 

 named from its supposed identity with the fossil ^^Choanites 

 KKnigiV (Proc. Zool. Soc. 1872, p. 123, pi. vi.), seems 

 to have been a variety of 8. crihrocrusta ; but if this should 

 not be the case, the illustrations of the " keratose sponge " 

 from South Australia, which he described from spirit-preserved 

 specimens in the British Museum in 1841 ('Annals,' vol. vii. 

 p. 129^ pi. iii.), are so undoubtedly! and to those, especially 

 that of the dermal crust in its " perfect state " (fig. 7), I would 

 refer the reader, for it is, as Dr. Bowerbank has stated of all 

 the rest, " beautifully and faithfully represented." 



It is strange that, in his description of Halispongia clioa- 

 7ioides, Bowerbank should have made no allusion to this 

 " keratose sponge," which is so typical of 8. crihrocrusta 

 that had he proposed a name for it, I should not have had to 

 introduce the one above mentioned; for the characters of 



