126 Mr. H. J. Carter on Fossil Sponge-sjnciiles of 



Thus the hexteniate head seems to take us from the Pachy- 

 tragife of the shore through the Coralliospongiffi of the com- 

 paratively shallow seas, down into the deep recesses of the 

 ocean, where, at 1913 fathoms, Dr. Wallich found the dimi- 

 nutive but important little sponge to which Dr. Wright (/. c.) 

 has given the name Wyville-Thomsonia WalUclin. Already 

 it will have been seen that M. de Pourtales found this (for 

 Stelletta [Tisi2)1wnia) agaricifonnis of Schmidt appears, mut. 

 mutand., to be identical with it) in 178 fathoms ; so that here 

 we have a sponge, in form and habitat respectively, connecting 

 the Pachytragige of the shore, through the Coralliospongise, 

 with the Calycispongiai (Kent) of the deepest seas. 



Figs. 37, 38, and 39, Plate IX., and figs. 72, 73, and 74 

 PI. X., are nail-like spicules, whose crucial or four-armed heads 

 as plainly sliow that they do not belong to the ternate as that 

 they do belong to a quaternate or quadrilid system, whose 

 parallel, as before stated, is only found in the spicules of Hy- 

 alonema {Carterm, Gray), 



On this, however, it may be observed that the minute 

 spicules with feathered shafts and quadrilid heads are not con- 

 fined to Ilyaloneiua, but are found also in lioltenia Caiyenteri, 

 W. Thomson (Phil. Trans. 1869, pi. Ixviii. figs. 9-11), and 

 in Pheronema Orayi^ Kent (Monthly MicroscojD. Journ., Nov. 

 1870, pi. Ixiii. figs. 9 and 10). So are there minute hexra- 

 diate spicules in many of the Coralliospongiee and Euplectel- 

 lidffi ; but Dr. W. Thomson states, respecting the former, 

 that " opposite to the point of junction of the vertical with the 

 four transverse rays there is frequently a more or less distinct 

 rounded elevation or tubercle. This undoubtedly represents 

 the sixth ray, the continuation of the primary axis of the sj)i- 

 cule " (Phil. Trans. 1869, p. 704) ; so that these feathered 

 shafts with quadrifid heads in lioltenia evidently belong to 

 the hexradiate system. But Avhere Dr. W. Thomson goes 

 on to state that in some cases " the tubercle is developed into 

 a branch, and the spicule becomes hexradiate, recalling the 

 ordinary hexradiate spicule of the sponge-mass oi. Ilyalonema^^ 

 I must join issue, inasmuch as I have never been able to see 

 such a tubercle in the minute spicules Avith feathered shafts 

 and quadrifid heads, nor in the large quadrifid spicules of 

 Hycdonevia^ although examined carefully for this purpose j nor 

 have I ever seen in any illustrations, or in my own examina- 

 tion of my mounted specimens of the sponge of Hyalonema., 

 any /icj^radiate spicules j while, as before stated, the simple 

 cross in the centre of the longer spicules, which was first 

 pointed out by Schultze (Ann. /. c), has always appeared to 

 me ^MarZ/-? radiate, as stated by him, and not Aeorradiate with 



