FOSSIL INFUSORIA IN IRELAND. 353 



spines in several places projecting through the substance of 

 the organic body which surrounds it, as at (a). It would, I 

 think, be a knotty point to determine, in this instance, which 

 of the two has been the aggressor, — the Ventriculite or the 

 Cidaris. The former cannot have been simply growing up- 

 on a dead shell, because the root of the zoophyte is at the 

 small extremity, and the large spines of the Echinus are still 

 in connection with the shell to which they belong. This cu- 

 rious fossil is in the cabinet of my friend Mr. Bowerbank. 



Art. V. — On Fossil Infusoria found in the County Down, Ireland. 

 By James L. Drummond, M.D., Professor of Anatomy in the 

 Royal Belfast Institution, President of the Belfast Natural History 

 Society. 



When my friend William Thompson, Esq., was at Newcas- 

 tle (at the base of the Mourne Mountains, County Down) last 

 autumn, he received a specimen of a very light, white, earthy 

 substance, which had been found some time previously in 

 considerable quantity, in that neighbourhood ; and a short 

 time ago he requested me to investigate its nature, as he felt 

 assured that it was the same kind of substance as Professor 

 Bailey had found in a bog at West Point, in America, (as 

 stated in Silliman's Journal for October, 1838), and which 

 was composed of fossil infusorial remains. I undertook the 

 investigation, and soon found that this anticipation was right; 

 the whole mass consisting of the siliceous remains of organ- 

 ized microscopic beings, either animal or vegetable. I am 

 not aware that fossil Infusoria have hitherto been detected 

 in the British islands, but if not, their discovery is due to Mr. 

 Thompson, as I have only followed up and ascertained, by 

 microscopical investigation, that the views which he had pre- 

 viously entertained were correct. 



The substance alluded to is, when dry, of the whiteness of 

 chalk, but becomes brownish when wet ; it is as light as car- 

 bonate of magnesia, which it much resembles, but is not act- 

 ed on by nitric, muriatic, or sulphuric acids, and is indestruct- 

 ible by fire. The specimen I received was a compact mass, 

 of the shape, and nearly the size, of an ordinary building- 

 brick ; it could easily be rubbed down into powder, and had 

 a coarse and somewhat fibrous fracture ; when a portion was 

 rubbed between the finger and thumb, it had no grittiness, 

 but felt like an impalpable powder, and when it was then 

 blown into the air, it flew about almost like wood-ashes. 



Vol. HI.— No. 31. n. s. 2 o 



