1867.] DR. J. S. BOWERBANK ON HYALONEMA MIRABILE. 21 



separated elongated fasciculi reposing on continuous membranes, 

 having the middle of the sponge perforated vertically by an extended 

 spiral fasciculus of single elongated and very large spicula, forming 

 the axial skeleton of a columnar cloacal system." 



I did not attempt any description of its specific characters, as my 

 object at that time was the description of generic characters only. 

 I now propose entering fully upon the consideration of the minute 

 structures of every part of this complicated and curious animal, and 

 to endeavour to give such descriptions of them as may serve to di- 

 stinguish it as a species from any other of its congeners. 



Hyalonema mirabile. Gray. 



Sponge. — JNIassive, sessile. Surface even. Oscula mammilloid, 

 more or less elevated ; terminations depressed, corrugated in radia- 

 ting lines, numerous, dispersed over the surface of a single central 

 elongated cloacal column projected from the middle of the sponge 

 upward ; dermis of the cloaca coriaceous, thick, composed of two 

 layers — outer layer arenaceous, inner layer spiculous; spicula acerate, 

 and cylindro-cruciform, apically or entirely spinous, various in size 

 and proportions : axis of the column a single large spiral fasciculus 

 of very long fusiformi-acerate spicida, each extending from its base to 

 near its apex ; spicula asperated near the base. Skeleton lamelli- 

 form ; spicula fusiformi-acerate, long and slender, apices obtusely 

 terminated; or fusiformi-subcylindrical. Defensive spicula: — exter- 

 nal inflato-fusiformi-acerate, hemispinous distally ; spines ascending. 

 Internal defensive spicula spiculated cruciform ; spicular ray as- 

 cendingly and entirely spinous ; cruciform rays spinous. Tension 

 spicula intiato-acerate, long and very slender. Interstitial spicula 

 attenuato-rectangulated, hexradiate, large and small ; and fimbriated 

 multihamate birotulate, in two systems : the primary one very large 

 and stout ; hami cidtcUiform, fimbriated at the base of the inner sur- 

 face ; shaft cylindrical, entirely tubcrculated, tubercles stout ; spicula 

 dispersed. The secondary system : — spicula smaller than those of 

 the primary one ; hami very long, apices nearly meeting ; neither fiar- 

 briated nor cultelliform, congregated. Interstitial spicula cylindro- 

 cruciform, terminally or entirely spined ; radii short and very stout ; 

 spines conical, acute, and very large. Retentive spicula fjuadri- 

 hamate, minute ; hami simple, elongate, attenuated. 



Colour, undetermiued in the living state. 



Hub. Japan. 



Examined in the dried state. 



The most perfect specimens I have seen are that in the British 

 Museum (which has the long spiral cloacal column immersed in the 

 basal mass of the sponge to very near its proximal extremity, as re- 

 presented in the Society's 'Proceedings' for 1857, plate ix., Ra- 

 diata), and two smaller ones now exhibited (sec PI. IV. figs. 1 & 2). 

 For the loan of the first of these I am indebted to my friend Capt. 

 C. Tyler, and for the second to the kindness and liberality of my 

 friend Mr. Henry Lee. One other specimen in a similarly perfect state 



