dredyecl up from the Gulf of Manaar. 55 



that of a Geodia, but the rest of the structure so totally dif- 

 ferent that, wherever located among the Holorhaphidota, it 

 must form a distinct group. The sponge not only grows 

 independently, as above stated, but also parasitically (that is, 

 laminiform over hard objects), yet always presenting the pla- 

 cophorous or mail-plated surface, which is already evident in 

 the smallest of the Manaar specimens, although it is extremely 

 thin and only 1-1 2th inch in horizontal diameter, with a cor- 

 respondingly diminutive form of the spiculation, indicating 

 not only that it is a very young specimen, but that the 

 ^partition of the plates from the commencement favours 

 its subsequent enlargement, and thus explains the mode of 

 growth. 



Besides this there is a species, or, rather, variety, in which 

 a spinispirular flesh-spicule is added to the foregoing spicula- 

 tion, consisting of a slightly sigmoid microspined shaft like 

 the flesh-spicule of Cliona corallinoides, whose spines after- 

 wards may become elongated, and sometimes multifid at the 

 extremity, so as to present the appearance shown by Dr. 

 Bowerbank (Proc. Zool. Soc. 1874, pi. xlvi. fig. 4). The 

 British-Museum specimen, of which I made a mounting in 

 Canada balsam some years ago, came from " Puntas Arenas " 

 in "Central America," and has been in the collection (as learnt 

 from the registration) since 1850. In my "Notes" I see that 

 it came "off a Gorgonia" while that described and called by 

 Dr. Bowerbank u Geodia carinata" (I. c. fig. 1), now also in the 

 British Museum, is on the same kind of black horny Gorgon ia- 

 stem from the "South Sea;" hence it is not impossible that 

 both may have come from the tropics ; but, be that as it 

 may, these are the only two specimens that I have seen in 

 which the spinispirula is present. It seems, however, to 

 afford corroborative evidence of this sponge being allied to the 

 Suberitida rather than to the Geodina ; for when the pin-like 

 spicules and the spinispirulas are seen together, in addition 

 to the structure generally, there is only one link left which 

 causes Placospongia to resemble the Geodina ; and that is the 

 siliceous ball ; so that the characters are far more in favour 

 of the Suberitida than the Geodina. Hence, as before stated, 

 the group of which Placospongia may be considered typical 

 should be placed among the Suberitida. I might here men- 

 tion that in the hilous depression of the siliceous globules 

 of my mounted preparations there is a plug of sarcode, 

 showing the way in which the former are connected with the 

 latter. 



