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XIII. — On a New Species of Fossil Xanthidium. 

 By H. H. White, Esq. 



Head December 21, 1842. 



In the paper which I had the pleasure of presenting to the Society 

 in February, 1842, upon the fossil Xanthidia, I described and figur- 

 ed, as the result of my observations, eleven species, exclusively of a 

 fossil animalcule abounding in flints, which I called globosum. Since 

 that time I have discovered another species, clearly distinguishable 

 from the eleven, and of which I beg to offer to the Society the follow- 

 ing description, accompanied with a drawing.* I class it as one of those 

 species called Tubifera ; but it differs from the three species of Tu- 

 bifera described in my former paper, in the following particulars : — 

 that the tentacula are longer, and instead of possessing any process at 

 their extremities, they gradually taper to the finest point ; the tenta- 

 cula apparent are from eleven to twelve, quite straight, and free from 

 any appendage whatever. This species measures about the -^^ of 

 an inch in diameter, including the extreme points of the opposite ten- 

 tacula. It is distinguishable from the Xanthidium spinosum, which 

 it in some measure resembles ; the tentacula of the latter are also ta- 

 pering to a fine point, but they are waving, irregular, much more nu- 

 merous, and without the tubiform appearance of the new species. I 

 think it is not advisable to alter the nomenclature already before the 

 public ; and although the species now under consideration might be 

 deemed the most simple in form of all the Tubifera, I would not sug- 

 gest a transfer of the name Tubiferum simplex from No. 10, in the 

 species described in my former paper, to the new species, but prefer 

 giving the latter the new name of Tubiferum spiculatum, forming the 

 twelfth species of the fossil Xanthidia. 



* Plate xx. fig. 4. 



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