Mr. H. J. Carter on the Hexactinellidae. 371 



that of the rest of the species characterized by the birotulate 

 spicule before mentioned), thus stands apart from all the other 

 sarcospiculous forms of Hexactinellidai possessing this spicule. 



Here I take the opportunity, in connexion with illustrations, 

 of correcting a mistake which I made respecting the anchoring- 

 spicules of Hyalonema ('Annals,' vol. xi. p. 280, 1873), viz. 

 that the specimen " half an inch long," which I took to be 

 Hyalonema^ I now find to be hollow, and, therefore, that it 

 cannot be one of Hyalonema^ but is probably one of Hol- 

 tenia Carpenteri. Hence, I still have not yet seen the free 

 termination of either the spiniferous or smooth anchoring-spicule 

 of Hyalonema] while those described (/. c.) in the young 

 Holtenia supposed to be Hyalonema show, as illustrated by 

 Prof. Thomson. (^. c), that the terminations of its spiniferous 

 anchoring-spicules are of two kinds, viz. one (the common form) 

 in which the Hukes are double and opposite, and the other in 

 which they are double or treble and all on one side, somewhat 

 resembling the laterally spined one of Euplectella (PI. XIV. 

 fig. 4). 



Then, again (at p. 284, I. c), I might have added what Dr. 

 Gray had sketched for me in a note long ago, viz. that the 

 broken spiral "bracket-like " line round the rough anchoring- 

 spicules of Hyalonema was crowned with short spines before 

 the latter became rubbed off (PL XIV. fig. 9) ; while they are 

 of the same nature as the spines on the shafts of the long 

 anchoring-spicules of Eu2)lectella, Holtenia^ and Meyerina, in 

 which species, as their spiral continuation disappears, the spines 

 become larger and moi'e isolated. 



The spines on the anchoring-spicules of Hyalonema are so 

 small and so easily detached (tig. 9,/) that we do not wonder 

 at their being for the most part absent on the exposed portions 

 of these spicules ; but on examining (this time) an un- 

 doubted specimen of Hyalonema about 1^ inch long in the 

 body, through which the cord passed, I found the spiral lines 

 on those parts of the spicules which were within the body all 

 fringed with the spines, and immediately mounted some in 

 Canada balsam for more deliberate examination, the result of 

 which went to show that the attenuated end of the sjjicule in 

 the conical part of the twisted cord which projects above the 

 sponge is smooth and nearly straight — that tlie spicule then 

 becomes undulated, and upon each bend appears a group of 

 minute points — that these, on descending, soon pass into short 

 spines, and that these become more prominent and supported 

 respectively on the bracket-like processes (PL XIV. fig. 9), 

 which, as before stated, form a broken spiral line, here and there 

 more or less continuous round the spicule (fig. 9, d) — till at last 



