STRUCTURE AND ECONOMY OF TETHEA. 405 



IX.— ON THE STEUCTUEE AND ECONOMY 

 OF TETHEA.* 



I am indebted to Mr. Guerin, one of my pupils, for the 

 specimens of the undescribed Tethea, to the structure and 

 economy of which I am about to direct the attention of the 

 Society. He procured them, along with many other speci- 

 mens, by dredging in deep water on the south-west coast of 

 Spitzbergen. They have been carefully preserved in alcohol, 

 and are in as favourable a state for examination as their 

 delicate texture will permit. 



These specimens present the globose or sub-globose form 

 peculiar to the group ; but two of them contract towards their 

 attachments, so as to resemble inverted cones, with spher- 

 oidal bases (Ti/thea turbinato-capita — Lamarck). 



The largest spherical specimen measured 4 inches in dia- 

 meter ; the smallest 2|. The turbinated specimens are 3 and 

 2£ inches long by 2| and 2 broad. 



Their colour is dark-grey when removed from the alcohol ; 

 but when in that fluid light lemon-yellow, on the dense, 

 fleshy, and more recently-formed parts of their surfaces, and 

 grey or dark grey where the downward and projecting spicula 

 abound, and where mud and debris, in greater or less 

 abundance, lodge in the crevices. 



The debris, or pellicle apparently exfoliate 1 from the 

 organism, appears to be entangled among the projecting 

 3picula on various parts of the surface in such a manner as to 



* Read before the Royal Society of Edinburgh, 7;h March 1853. 



