6 Mr. H. J. Carter on the Suhspherous Sponges. 



short conical processes standing out vertically from a thick 

 globular body. Size variable ; that of the specimen figured 

 3 inches in diameter. Colour : grey on the surface, yellowish 

 interiorly. 



Hob. South-east coast of Arabia, opposite the north-east 

 end of the island of Masira. Free at the bottom of the sea, 

 whence it gets landed by the waves. 



Ohs. I have never found a living specimen of this sponge, 

 or a specimen fixed to the rocks : my descriptions are taken 

 from dried ones found on the sea-shore, whose shape never- 

 theless indicates their free or floating habit. Pieces of stone 

 and coral, however, may be attached to this sponge almost 

 sufficient to keep it stationary at the bottom of the sea ; and in 

 these instances it is observed that the crust is always con- 

 tinuous next to the foreign material, by which we learn that it 

 must therefore have been the dermal sarcode outside the cnist 

 which attached them to the surface of the sponge. Of course 

 the same remark applies to the condition under which portions 

 of O. aralnca would float or sink to the bottom as that on T. 

 arahica^ viz. the presence or absence of air in it. 



This species is closely allied to Geodia zetlandica of our 

 shores ; and if hereafter it should be found that the dermal 

 spicules of G. arabica are of the same kind as those which 

 impart a like hirsute character to G. zetlandica^ and that this 

 character in the latter should be owing more to their presence 

 than to the " projection of the body-spicules " (which in G. 

 arahica are ten times as long as the dermal ones), then it is 

 not improbable that both will have to be regarded as belong- 

 ing to the same species. Stellate spicules also abound in the 

 dermal sarcode, but they are subsidiary ; they are no more 

 numerous there than the stellate spicules which we shall pre- 

 sently see in the dermal sarcode of Pafhymatisma Johnstoma^ 

 where a fusiform, rough, and not the stellate form will be 

 found to be the dermal spicule in particular. Like the latter, 

 whose surface, when fresh, is of a grey colour, from the trans- 

 lucent state of the globular crystalloids and sponge-tissue 

 when soaked in water, it consequently becomes chalky-white 

 when dry ; and probably, like Pachymatisma also, although 

 subsequently free, is, in tlie early part of its history, fixed in 

 some submarine locality. 



On comparing the size of the pores and their distance apart 

 in G. arahica with those in a fresh specimen of Pachymatisma 

 (where tliey a-p])ear in other respects to be ])recisely alike), I 

 find that tin*, former are all much smaller and much nearer 

 togctlicr than in the latter. But as they are much smaller 

 and much nearer together in the dried than in the fresh spcci- 



