Ehrenberg on Infusoria in Igneous Rocks. 413 



stone contain infusoria, and I think I forwarded several, with their 

 localities marked.* The formation is on a grand scale ; it contains 

 much gypsum, it has the consistence of our chalk, but is perhaps 

 somewhat softer, and it has an enormous extension. At Port St. 

 Julian it cannot he less than 800 feet thick. Its average breadth is 

 at least 200 miles, and probably more, while it extends from north 

 to south at least 550 miles." 



The author on this renewed his investigations with every possible 

 attention, and communicates the result, enumerating the species and 

 their localities. The number of species described amounts to thirty ; 

 but he states that every fresh investigation has increased this num- 

 ber, and has also tended to confirm the volcanic character of the 

 rock.f 



These thirty organic bodies, associated with very minute frag- 

 ments of cellular glassy pumice greatly resembling them, so com- 

 pletely make up the whole mass of this Patagonian rock, especially 

 at New Bay, that either the shells or fragments of them can be 

 detected in every little morsel not larger than a pin's head. It is 

 also perfectly clear that they have been subjected to a high tempera- 

 ture, which has burst them asunder, bent, polished and altered them. 

 It is even probable that the glassy crushed fragments are also de- 

 rived immediately from these organic products ; but there are here 

 and there, besides these, green crystals resembling augite. 



This mass chiefly consists of species which inhabit salt water, and 

 of these many have been long known and are widely extended 

 through the ocean ; but several of them are new and peculiar, and 

 resemble in shape small stars. Nearly half of them are the siliceous 

 particles of marine sponges whose forms are known, and of which 

 we are in some cases acquainted with the origin. 



The Patagonian rock thus described is therefore manifestly a sea- 

 bottom which has been subject to volcanic action. 



• The author had found these remains in all the specimens, 

 f The species of Polygastrica (infusorial animalcules) amount to seventeen, 

 and the Phytolitharia are thirteen. They are thus distributed :— 



Polygastrica. Phytolitharia. Total. 



Port St. Julian 10 8 18 



Port Desire 13 7 20 



New Bay 2 1 3 



