two senera, Holtenia and Pheronema, whose bodies are 

 somewhat similarly cup-shaped, but have the rope-like 

 bundle of spicules, that in Hyalonema form a simple stalk, 

 distributed singly or in small fascicles throughout the 

 entire external surface. In Pheronema Grayi in particular, 

 obtained by the writer in the year 1871, in connection 

 with the dredging expedition of the yacht " Norma," from 

 a depth of 600 to 800 fathoms, off the coast of Portugal, 

 these filaments, the so-called anchoring spicules, are so 

 thickly developed from the sponge body, and are of such 

 extraordinary length, that the organism presents the ap- 

 pearance of a light blonde wig. Several specimens of this 

 type, known to the local fishermen by the title of the. 

 Portuguese birds'-nest sponge, have been presented by 

 the writer to, and are now on view in, the new Natural 

 History Museum. A curious and hitherto undiscovered 

 form belonging to the same group, the hat sponge {Asko- 

 iierna Setiibalense, S.K.), obtained by the writer from the 

 same locality, is composed chiefly of long thread-like 

 silicious spicula, felted together in such a manner as in 

 both shape and dimensions to closely resemble a very 

 shabby grey flannel boating hat. 



All of the several silicious sponges just described, in- 

 cluding the Euplectella, or "Venus's Flower Basket," the 

 glass-rope, birds'-nest, and hat sponges share, in common, 

 the circumstance that the silicious spicules of which their 

 skeletons are composed belong, more or less extensively, 

 to what is known as the hex-radiate type, that is, are 

 composed of six rays, and are hence as a family group 

 distinguished by the technical title of the Hexactinellid(B. 

 It is an interesting fact that the fossil sponges of the chalk 

 formations, familiarly known as Ventriadites, exhibit similar 

 structural composition, and were in like manner inhabitants 



