B. W. PRIEST ON THE HEXACTINELLIDJ 5 :. 11 



conical sac, is enveloped in a bunch of white horse-hair-like, long, 

 anchoring spicules, respectively smooth and spiniferous, with hooks 

 at the free extremity of the latter. 



" The flesh spicule, a rosette many-rayed ; rays of equal length, 

 sigmoid, clavate, and dentate outwards, claw-shaped, flexed and 

 grouped en fleur-de-lis, or with rays of equal length, straight 

 and pointed ; occasionally with straight rays, few, and terminated 

 by three or more spines at the free ends laterally." Those with the 

 claw-shaped rays, or, as the late Dr. Bowerbank called them, the 

 florocomo-sexradiate spicules, are found on the outer surface of the 

 sponge, immediately beneath the dermal membrane, cemented to 

 the apex of the distal portion of the central shaft of the spicules 

 forming the beautiful quadrangular network surrounding the sponge. 

 Specimens are difficult to obtain with these spicules in situ, as the 

 majority of the sponges have been well washed before they come into 

 our hands. When the first specimens of Euplectella were brought 

 to England there was some little contention regarding its place in 

 Natural History, some supposing, along with the fishermen who 

 dredged them, that they were formed by some species of Crustacean 

 as many were found with crabs in their interior ; but how came the 

 creatures there? Once in, they could not escape, and then again it was 

 not always the same species that was found in them. Some naturalists 

 thought that the sponge belonged to the Alcynoid family, forgetting 

 the presence of the polyps which characterize an Alcyonia. At last 

 it was decided that the Euplectella was a sponge, and that the crabs 

 must have obtained eutrance when both were in a young stage, and 

 had grown up together. The base of Euplectella has often much 

 sand and extraneous matter attached to the glassy filaments which 

 yield very rare Foraminifera and other minute organisms. 



I will now just draw your attention to the skeleton framework of 

 Farrea and Aphrocallistes, both being comprised under the same 

 family as Euplectella. 



The Farreas are sponges more or less tubular and branched ; 

 branches open, and slightly expanded at the free extremities ; walls 

 thin, of only one layer. 



Aphrocallistes is also tubular and branched ; branches closed at 

 their free extremities ; wall thick and formed of polyhedrally reticu- 

 lated fibre. 



In some of the members of both may be found a scopuline spi- 

 cule distinguishing the species. 



