1875. ] SILICEO-FIBROUS SPONGES. 279 
smoothness of the skeleton and the well-developed system of canals 
in the fibres at once distinguish this species from either F’. occa 
or Ff. spinulenta. It is remarkable that the sponge appears to con- 
sist of a single layer only, as I could not find the slightest trace of 
any other siliceo-fibrous structure on any part of the specimen. 
Mr. W. Saville Kent has evidently mistaken this species for Far- 
rea occa in the description he gives of that species in the ‘ Micro- 
scopical Journal’ for Nov. 1870, p. 248, plate Ixiv. figs. 12-18; 
and he has correctly figured the central canals in the dermal net- 
work of his specimen (fig. 13), whereas in the corresponding organs 
of Farrea occa no such canals are visible. The description of the 
sponge represented in the same plate by fig. 12 is quite in accord- 
ance with the small fragment of the species F’. devis that I re- 
ceived from Mr. Lee. Mr. Kent writes, “The skeleton of this 
sponge is composed of a series of infundibular netted tubuli branch- 
ing out from one another and occasionally coalescing.”’ The branch- 
ing fistular form represented by Mr. Kent in fig. 12, plate Ixiv. 
‘ Microscopical Journal’ for Nov. 1870, occurs also in F’, tubulata, 
very much in the shape represented by Mr. Kent; but the other 
specific characters differ to a very considerable extent from those of 
F. levis. I received this sponge from my late friend Mr. H. 
Deane, along with the specimens of Farrea gassioti and pocillum ; 
and I presume it is from the same locality as those species. 
FARREA PARASITICA. 
Sponge parasitic, coating. Surface irregular? Oscula, pores, 
and dermal membrane unknown. Skeleton-rete irregular; fibres 
depressed, occasionally confluent, very irregular in breadth ; canals 
distinct, variable in diameter, not always confluent, but usually so. 
Colour translucent as glass. 
Hab. West Indies (Captain Hunter, R.N.). 
Examined in the skeleton state. 
During the course of my examination of the beautiful little speci- 
men of Farrea gassioti, I observed on the inner surface of the sponge 
several small thin patches of siliceo-fibrous tissue, very much finer 
in structure than the skeleton of the sponge to which they were 
attached. On removing small portions of these tissues and mount- 
ing them in Canada balsam I found them to be strikingly different 
in all their specific characters from the sponge on which they re- 
posed, and especially so in the size of their skeleton-fibres—the 
average diameter of those of F. gassioti being 74,5 inch, while those 
of F. parasitica was +3\;s inch ; and the canals in the former species 
averaged ;/,, inch in diameter, while in the latter one their average 
was y;/5 inch. These discrepancies, if there were none other, di- 
stinctly separate them as species, although in such close contact in 
their natural condition. I could not, with a power of 100 linear, 
detect any indications of a natural dermal surface, nor could I by 
any means find portions of dermal or interstitial membranes or of 
sarcode ; our sole dependence, therefore, is upon the structural pecu- 
