336 Mr. R. Hope on two new 



the spicules in one particular, namely, that in the latter the 

 turn of the spiral is usually more or less compressed laterally ; 

 that is, the imitation would be closer, if we suppose the pencil 

 to have an elliptical instead of a circular section and the wire 

 to be laid along one of the thinner ends of the ellipse at right 

 angles to the long diameter. 



The central twist of these toxa is admirably shown in a 

 photograph from one of my preparations of the sponge, for 

 which I am indebted to the kindness and skill of my friend 

 Mr. J. Howard Mummery, F.R.M.S., and of which the 

 figure A, 8 is a copy. 



The smaller toxa (fig. A, 7) do not show this central twist, 

 but neither do they lie in one plane, one turn of a very slack 

 spiral apparently being completed in the whole length, or 

 nearly so, of the spicule. 



The only other sponge which, so far as I know, possesses 

 this (that is, the long-armed) form of toxite is Amphilectus 

 foliahts (Vosmaer), Bowk, {^= Halichondria foliata, Bowk., 

 Mon. Brit. Spong. iii. p. 198, pi. Ixxiii. figs. 1-5, and iv. 

 p. 106 ; and Carter, Ann. & Mag. Nat. Hist. (4) 1876, xviii. 

 p. 310, pi. xiii. fig. 10, and pi. xv. figs. 29 a, 5). Hali- 

 chondria mutulus, Bowk. (Mon. Brit. Spong. iii. p. 209, 

 pi. Ixxiv. figs. 4-8, and iv. p. 96), in which this toxite is 

 also found, has the same spiculation as A. foliatus ; and 

 examination of the type preparations (there is no type speci- 

 men of H. mutulus) in the British Museum leads me to con- 

 clude that, if not the same sponge, which I think they are, 

 the two forms must be considered merely as varieties of the 

 same species. 



Through the kindness of Mr. Carter in lending me his 

 prej^aration of A. foliatus from the N.W. coast of Shetland 

 [op. et loc. cit.) I have been enabled to examine its spicula- 

 tion and compare it deliberately with that of M. strepsitoxa. 

 The toxites of the former are a little longer on the average and 

 convey an impression of more luxuriant growth — that is, they 

 are frequently flexuous, and the central twist is often sharper 

 and not seldom even reversed, so as to form a loop, as 

 described by Dr. Bowerbank {op. cit. iii. pp. 200 and 211) 

 and figured by Mr. Carter [l. c. pi. xii. fig. 10 b) ; the spiral 

 also is often more compressed laterally, and in some few cases 

 it is doubtful if it is present at all. With these slight modifi- 

 cations the spicule is identical in the two species. 



In his description of Halichondria foliata (Ann. & Mag. 

 Nat. Hist. I. c.) Mr, Carter mentions that the tricurvate of 

 that sponge was also found in Microciona armata^ as he knew 

 from a specimen taken at Budleigh Salterton ; it is clear that 



