188 A MONOGRAPH OF THE 



mal membrane pellucid, furnished abundantly with 

 large spicula, same as those of the skeleton. Skeleton. 

 Spicula abundant, fasciculated, fusiformi-acuate, large 

 and long. Tension spicula acuate, very minute and 

 slender. Retentive spicula bihamate, simple and con- 

 tort, dispersed, minute, very abundant ; also dentato- 

 palmate, unequi-anchorate, large and small; large 

 ones congregated in rosette-shaped or globose groups ; 

 occasionally dispersed ; small ones dispersed. 



Colour. — In spirit and dry, pallid gray. 



Locality. — Western Islands, Scotland, Mr. Archibald 

 McNab ; Outer Skerries and Unst, Shetland, Mr. C. W. 

 Peach. 



Examined. — In the condition it came from the sea, and 

 preserved in spirit. 



I received three specimens of this sponge from Mr. 

 Archibald McNab, a fisherman at Inverary. They are of 

 nearly equal size and form, about three inches in length by 

 one and a half inches in width, and from half to three 

 fourths of an inch in thickness ; very nearly resembling in 

 form a similar length from the distal end of the tongue of 

 a sheep. 



When in the imdried condition the sponge is exceedingly 

 soft and flaccid, and it was with considerable difficulty I 

 could detect the oscula, in consequence of the collapsed 

 condition of the sponge. It does not contract much in 

 drying, and when in that state it strongly resembles a mass 

 of chopped tow, which has been compressed in the hand 

 while wet and dried in that form. 



The structure of the skeleton is obscure ; in many parts 

 the spicula, especially towards the edges of the interstitial 

 membranes are so numerous and so closely packed toge- 

 ther as to assume the form of fasciculi, and in some measure 

 that of the skeleton of a Halichondria; but there are no 

 distinct angular junctions forming an irregular network, as 

 in even the most indistinct species of Halichondria. 

 The fusiformi-acuate spicula of the skeleton have many of 



