350 DR. BOVVERBANK ON HYALONKMA MIRABILE. [Mar. 28, 



Fitis. The anterior extremity of the dorsal is midway between the 

 saout and base of caudal ; whilst the ventral is under its centre. 

 Anal is situated in the posterior fourth of the body. The caudal 

 has a broad base, and is lobed in its posterior half. 



Colours. Rifle-green, with a bluish-green stripe along the centre 

 of the body and middle of the caudal fin. Abdomen greenish yellow. 

 Fins yellow ; dorsal, pectoral, and ventral externally stained darkish. 

 Edges of scales darker than their centres. Eyes golden. 



Hub. Wynaad, in rapid streams. 



6. Additional observations on Hyalonema mirabile. 

 By J. S. BowERBANK, LL.D., F.R.S., F.Z.S. &c. 



Since my paper on Hyalonema mirabile, read January the 10th 

 at the Zoological Society, I have been favoured by my friend Mr. 

 Henry Lee with the loan of a specimen of that species singularly 

 illustrative of the nature and structure of the corium, the outer coat 

 of that organ having little or no sand or other extraneous matter 

 imbedded in it. At the first view this singular specimen might 

 readily be mistaken for a new species, the thin smooth corium quite 

 destitute of sand gives it an appearance so very unlike the usual 

 description of specimens ; but a close examination of its structural 

 characters quickly disabuses us of this idea. The cruciform and other 

 spicula imbedded in the corium ; the spiral column and the other 

 structures of the basal mass of the sponge, are identical with the 

 corresponding structures of the well-known specimens of Hyalonema. 

 It is the absence of the usual sand which alone makes the difference 

 between them, and at the same time greatly I'acilitates our knowledge 

 of the structures of these curious animals. 



The whole of the corium in Mr. Lee's specimen is divided into 

 lozenge-shaped areas of various sizes, a thin protuberant line forming 

 the common boundaries of the adjacent areas ; at each side of this 

 line the motive filaments are based, and from these points they pass 

 in direct lines to the protuberant osculum in the middle of the area, 

 passing up the sides, and on to the apex, where they terminate in a 

 ring formed by the outer margin of the apical membrane of the os- 

 culum. The fibres are broad and flat at their bases, gradually at- 

 tenuate in breadth and slightly increase in thickness as they approach 

 their distal terminations. 



Two of the oscular bodies which were raised but very little above 

 the surface of the corium, when mounted in water, exhibited the 

 radial arrangement of the fibres in their natural condition in a very 

 satisfactory manner : fort3f-four were counted ; but this was evidently 

 not the whole of them, as many others were indistinctly apparent 

 behind those which were counted. \n another specimen in my col- 

 lection which has been soaked in solution of potass I counted sixty- 

 three ; and in one of the large areas containing an osculum in Mr. 

 Lee's specimen I counted ninety-six motive fibres, radiating from the 



