BPONGIIBA. 431 



straight, sharp, slender, about "002 miHim. long at head, where 

 they are closely aggregated, gradually decreasing in size and 

 numbers towards point, where they cease entirely ; size of spicule 

 •1 to -17 by -0063 to -0079 millim. (2) Hastate cylindrical or 

 subacerate, smooth, of almost uniform diameter from centre to 

 within two diameters of ends, whence it tapers to a sharp point ; 

 size -2 by "0042 millim. Plesh-spicule, (3) Equianchorate ; tri- 

 dentate, with stout, strongly backwardly curved shaft "0026 mUlim. 

 in diameter; lateral arms of heads subtriangular, about -0068 

 millim. long, the middle of the margin of the arm conspicuously 

 folded inwards ; the middle arm narrow, oblong, about "0032 mUUm. 

 long ; length of spicule -025 miUim. 

 Hah. Port Jackson, to 5 fms. 



The entire " stock " or head, of which the single well-preserved 

 spirit-specimen consists, is 42 millim. (1| inch) in height by 40 

 in greatest diameter ; the individual branches may be as much as 

 9 millim. in diameter at their broadest palmate part. I am under 

 the impression that this is the species alluded to by Mr. Carter 

 Q. c.) as Haliehondria plumosa, from Kerguelen Island. It differs, 

 however, in spiculation from the typical form of that British spe- 

 cies in having the shaft of the anchorate about twice as thick and 

 in the longer and slenderer hastate spicule ; the difference between 

 the anchorates is perceptible even under a low magnifying-power. 

 It is, however, nearly allied to both it and Myosilla fiatitia of 

 Bowerbank, and to some Mediterranean Myieillm of Schmidt. 



I add the measurements of the spicules of what is probably the 

 type specimen oi Halichondria (Microdona, Hk.) plumosa, Mont., for 

 comparison : — 



1. Spined aouate, "16 by -0063 millim. 



2. Hastate acerate (hastate only ^t one end), '17 by -0063 

 millim. 



3. Equianchorate, -016 millim. long, shaft -0013 millimw in 

 diameter. 



Mr. Carter places species of this nature in a new Group, called 

 PlumdhaHchondrina (Ann. & Mag. Nat. Hist. 1875, xvi. p. 144, and 

 1880, vi. p. 39), as being distinguished by their habit and their an- 

 gulated, not " naviculiform " anchorate ; but his genus Plumohali- 

 ehondria{op.cit. 1876, xviii. p. 236) must be carefully distinguished 

 from this similarly named Group, for it is described as possessing a 

 naviculiform anchorate. 



CBELLA. 



Orella, Gray, P. Z. S. 1867, p. 621. 

 Cribrella, Schmidt) Adr. Meer. p. 69. 



Schmidt's generic name was already in use for a genus of 

 Asteridean Echinodermata (L. Agassiz, 1835, Mem. Soc. Sci. Neuf- 

 chatel, i. p. 191). Dr. Gray therefore very properly altered it. 



The present species, although the first assigned to the genus from 



