160 A MONOGRAPH OF THE 



Colour. Dried, light fawn or cream-colour. 

 Habitat. Stroma, Shetland, Mr. C. W. Peach. 

 Examined. In the dried state. 



At the first glance at this sponge, with a two inch lens, 

 the student might readily mistake it for a dried coating 

 specimen of Halichotidria panicea, the reticulated surface 

 of each so closely resembling the other ; but the pecu- 

 liarities of the oscula areas will quickly remove such an 

 erroneous impression. These organs are remarkable in 

 their characters. In some of the areas five or six oscula of 

 various sizes are congregated, while others contain but a 

 single osculum. The margins of the areas are slightly 

 elevated, and are thin at the edges, and for a short distance 

 surrounding them the reticulations of the dermal membrane 

 are obsolete, and in their places we find the spicula ar- 

 ranged in nearly parallel lines, converging towards the 

 margin of the area, rendering the tissues close and dense 

 in their structure. The same arrangement prevails around 

 the margins of the single oscula. The reticulations of 

 the dermal membrane are very irregular in size, and the 

 spicula of the network far too numerous to be counted. 

 In other respects, the tissues of this sponge are extremely 

 simple, the spicula of all parts being of the same form, but 

 somewhat variable in size. 



The sponge covers a surface of about one and a half 

 square inches, and does not exceed about two lines in 

 thickness. It is seated on a portion of a flat boulder, and 

 was dredged by Mr. J. Gwyn Jeffreys, at Shetland, in 

 1864, and preserved for me by my friend Mr. Peach, who 

 accompanied the expedition. 



gJHymeniacidon fallaciosus, Bowerbank. 



Sponge. Sessile, coating fuci or zoophytes. Surface 

 smooth, minutely reticulated. Oscula simple, dis- 

 persed. Pores inconspicuous, Dermal membrane 

 translucent, spiculo-reticulate ; rete irregular, multi- 



