Notice of Ehrenberg^s Memoir on Microscopic Life. 307 



he thinks they must have changed into the fine siliceous sand, 

 which is present in these ochres. 



Maine. — Lists of the fossil infusoria from two different de- 

 posits discovered in 1838, near Blue-Hill Pond, in Maine, by Dr. 

 Charles T. Jackson, are given. Both specimens were of a chalky 

 whiteness, and all the forms, with the exception of various Spon- 

 giolites, (which are particularly abundant in one sample,) are 

 decidedly fluviatife. Ehrenberg remarks on the difficulty of de- 

 cision caused by the presence of these apparently marine spiculae 

 of sponges, and says : 



" We may ask, if the formation is marine, why are no Coscinodisci, 

 Actinocycli, &c. to be found ? Perhaps it is a deposit from brackish 

 water which in the neighborhood of the sea still contains some species 

 of sponges." 



As these Spongiolites suggest similar remarks by Ehrenberg 

 with regard to various localities, we would state, that there can 

 be no doubt that they are certainly of fresh-water origin, although 

 some of them have much resemblance to some marine forms. 

 The circumstances under which they occur in numerous locali- 

 ties, hundreds of miles from the sea, and in the most recent de- 

 posits of bogs and streams, leave no doubt of their fluviatile origin. 



The notice of the species observed from Newfoundland, Lab- 

 rador, Kotzebue's Sound, Iceland, and Spitzbergen, we are obli- 

 ged to omit. 



In concluding this enumeration of American localities, Ehren- 

 berg remarks : 



" That the extent and influence of the minuter American forms of ani- 

 mal life now known to him does not terminate here. At the above men- 

 tioned localities, the forms are chiefly siliceous, but microscopic calca- 

 reous organisms have also a most important development in America." 



Allusion is then made by the author to the vast extent of the 

 cretaceous formations on the American continent, as shown by 

 Dr. Morton's Synopsis of the Cretaceous Group, and Von Buch's 

 splendid Memoir on the Petrifactions collected by Humboldt in 

 America. Ehrenberg then observes : 



" Since the Academy was informed in 1838 that by a peculiar method 

 of observation, it is possible to prove that all writing chalk and many 

 compact calcareous rocks, result from the agglomeration of invisible 

 Polythalamia, this method was applied in 1841 by Prof. Bailey to the 

 cretaceous rocks of North America, and the same results obtained.* 



* See this Journal, Vol. xli, p. 213 and p. 400. 



