Hexactinellidse and Lithistidte. 455 



viz. figs. 1 &7, we shall find by-and-by to belong to two different 

 species of Farrea, both figured previously and separately by 

 Prof. Owen (op. et loc. cit. figs. 8 & 9 respectively) ; while 

 Dr. Bowerbank's figure 7 alone represents Farrea occa, and the 

 " retentive spicula " belong to quite another and very different 

 system of sponges. 



Now, considering that Dr. Bowerbank viewed fig. 7 as the 

 " harrow-like tissue of the dermis " of some unknown sponge 

 (instead of a part of the skeleton itself, which we now know 

 to be the case) — that is, a portion of the wall itself of the tube 

 of which Farrea occa is formed — considering that the term 

 "fistulose" for the fibre, as being analogous to "simple 

 keratose fibre " (B. S. vol. i. p. 80), ex. gr. Luffaria, is mis- 

 applied, inasmuch as it will presently be shown that the fistu- 

 lous appearance in the siliceous fibre arises from the presence 

 of sexradiate spicules, while in the keratose fibre it is a bond 

 fide continuous canal — and considering that the " attenuate 

 stellate retentive spicula " are not of the sexradiate type, but 

 probably belong to an undescribed species of Gummina (see 

 • Annals,' 1873, vol. xii. p. 22), we have absolutely nothing 

 left but the fragment of rectangular, vitreous, lattice-like fibre 

 of this sponge, first represented by Prof. Owen's figures 9 & 9 a 

 (op. cit.), and repeated in Dr. Bowerbank's figure 7 (P. Z. S. 

 l.c). 



That, however, this rectangular lattice-like vitreous fibre 

 has been identified with that forming the skeleton of a sponge 

 to which Mr. Kent has applied the name of Farrea occa in his 

 figures (I.e.), confirmed by my own observation, his delineations 

 will show, and the specimen itself (now, Mr. Kent informs me, 

 in the British Museum) will demonstrate. But there was 

 nothing but the skeleton left, which, as before stated, was 

 dredged up on the coast of Portugal filled with mud. Mr. 

 Gassiot's specimen, of which I made an accurate drawing and 

 microscopical examination, was in the same condition, and 

 the specimen in " No. 3 a," dredged up on board H.M.S. 

 ' Porcupine,' also the same ; while Schmidt's figure of the 

 specimen from Florida, which he examined (op. et loc. cit.), 

 does not differ from either, and appears to have been also 

 nothing but a deciduous skeleton, although it was accompanied 

 by the spicules mentioned, and Schmidt has made a new species 

 of it under the name of u Farrea facunda." 



Since the above was written, I have (as before stated) ex- 

 amined Dr. A. Farre's specimen of Euplectella cucumer, 

 entangled in the beard-like mass of which at the base (viz. the 

 long anchoring-spicules) are many large fragments of Farrea 

 occa (PI. XVI. fig. 4), among which is a small portion of the 



