65 



The characteristic difference of this genus, and by which 

 it is proposed to separate it from alcyonium, is the diverging, 

 radiating, internal fibres, being collected in fasciculae. 



From the description of this genus and of some of its 

 species, there does not appear to be any reason for sup- 

 posing that it may not be as susceptible of those changes on 

 which petrifaction depends, as some of the species of al- 

 cyonia are known to be. Fossils indeed, resembling in form 

 tethya lyncurium, (Orange du Mer) figured by Marsilli, 

 Donati, and Esper, are not infrequent among the assumed 

 fossil remains of alcyonia. 



Geodia. A free, carnose, tuberiform polypifer, hollow 

 and empty, and firm and hard when dry ; the outer surface 

 being all over porous ; and has on the side a separate cir- 

 cular area, pierced with large pores. 



This animal is perhaps described only by Lamarck, who 

 had seen but one specimen of it, which he purchased at the 

 sale of the cabinet of M. Turgot, Governor of Guiana : no- 

 thing has been stated respecting its existence in a fossil state. 



Palythoa. M. Lamouroux has very properly formed a 

 genus for the reception of two animals which Solander had 

 placed among the alcyoniums, but which differ from that 

 genus in manifesting more complexity of organization ; the 

 cavities, which are distinct, are divided by longitudinal la- 

 mellae, being each appropriated to a single polype. 



Palythoa. A polypifer, flat, covered with numerous, cy- 

 lindrical, united mammillae, of more than a centimetre in 

 height, with isolated cavities or cellules, almost longitudinally 

 chambered, and each containing a single polype. Lam. 



Sp. 1. P. mammillosa. The polypiferous cellules with a stellated 



opening. Sol. and Ellis, p. 179, n. 5, Tab. i. fig. 4, 6. 

 2 ocellata. Rugous mammillae ; opening stellated and ra- 

 diated, Sol. and Ellis, p. 180, n. 6, Tab. i. fig. 6. 

 A sketch of this species in its recent state, from Ellis, is given 

 Plate i. fig. 14. 



