EEPOET ON THE KERATOSA. 25 



found as to the question of whether the upper skin of the representatives of this latter 

 genus is to be drawn oflf easily or not, and that this is due both to the state of preserva- 

 tion and to the number of foreign bodies in the dermal membrane ; and when I finally 

 lay stress upon the fact that Dr. Marshall makes no positive statements as to the internal 

 structure of his genera Psammascus and Dysidea, so that these forms, like the species 

 Dysidea coriacea of Bowerbank and Dysidea fragilis, Hyatt, perhaps all belong to the 

 family of Spongidae, or are to be distributed in different families of Spongidse and 

 Spongehdse ; — then the reader will see that after Dr. Marshall's paper the matter becomes 

 comparable with the Gordian knot, which can no longer be disentangled but only cut 

 asunder. This I perform in the following manner. I unite the genera Psammascus, 

 Dysidea, and Spongelia into a single genus Spongelia, characterising it by large flagellated 

 chambers — of course, as in the whole family, devoid of any special cameral canaliculi — 

 and by the tendency to form " conuli." 



Psammoclema. 



This genus of Dr. Marshall ^ I adopt for the forms with small flagellated chambers 

 and wdth the external surface smooth and devoid of any projections of the skin owing 

 to those of the skeleton. All this is only of a temporary character ; indeed, the 

 possibility is not excluded that many good species, still undoubtedly allied amongst 

 themselves, are all alike in the possession, for instance, of the character of forming 

 cylindrical tubes with a weU-developed central cavity, so that my species Psammoclema 

 vosmaeri would have to be transferred into another new genus ; but it must be remem- 

 bered that in the group Keratosa all the present arrangements are but of a provisional 

 character. 



Psa7nmoj)emma. 



This genus, established by Dr. Marshall,^ admits of a very sharp diagnosis. Among 

 its representatives no horny skeleton is to be found at all, the propjjiug apparatus of 

 the sponge being represented by foreign enclosures exclusively. Moreover, the genus is 

 perhaps really a good one, since, as suggested by Dr. Marshall, the possibility is not 

 excluded that the sponges in question receive the foreign bodies in a way different from 

 that in which they are obtained by other Spongelidaj (comp. Dr. Marshall's above- 

 mentioned paper, p. 121). At any rate, this genus is to be referred to the Keratosa,^ and 

 according to the internal organisation of the soft parts to the Spongelidae. 



> Loc. cit, p. 109. - Loc. cit, ji. 113. ^ For grounds, see p. 46. 



(ZOOL. CHALL. ESP. — PART XXXI. — ISSi.l Hh i 



