168 ANATOMY AND PHYSIOLOGY 



marginal cavities separate, symmetrical, subcylindri- 

 cal ; each furnished with a membranous valve at its 

 proximal extremity. 



Type, Geodia gibberosa, Lamarck. 



The genus, as described by Lamarck,* is so loosely 

 characterised that I have thought it better to reconstruct it 

 entirely than to endeavour to amend it. I have therefore 

 given a new series of characters, founded solely on its 

 structural and organic peculiarities. I am acquainted with 

 seven species, all of which perfectly agree in the essential 

 generic characters as thus constructed. 



The type specimen of Lamarck's Geodia gibberosa in the 

 Museum of the Jardin des Plantes of Paris, the organiza- 

 tion of which, through the kindness of Professors Milne- 

 Edwards and Valenciennes, I have had an opportunity of 

 thoroughly examining, is unfortunately in so deteriorated a 

 condition in many respects, and especially in regard to the 

 dermal membrane and pores, that I have been induced to 

 select G. Barretfi from which, to a great extent, to describe 

 the interesting and highly organized structures of this 

 genus ; and I have the advantage also in this species of 

 having a portion of a specimen which has never been de- 

 teriorated by drying, having been pickled in strong salt 

 and water immediately on being taken from the sea, by 

 my friend Mr. McAnclrew. and in this state it closely re- 

 sembles a mass of somewhat indurated animal liver. 



The skeleton is composed of continuous fasciculi of stout 

 long spicula, which in massive specimens radiate from the 

 base to the outer surface of the sponge ; or if the species 

 be of an elongated form, from the central axis to the cir- 

 cumference, where in either case they terminate at the inner 

 surface of the crustular clermis, intermixing with, and 

 being firmly cemented to, the shafts of the expando-ternate 

 connecting spicula, which are attached to and firmly support 



* " Polyparinm liberum, carnosum, tuberiforme intus cavum et vacuum, in 

 sicco durum ; externa superficic uiiclique porosa. Foramina poris niajora in 

 area unica orbicularo et laterali observata." (Lamarck, ' Ann. s. Vert.,' 2de 

 edit., ii, 593. 



