297 



produced by a Silicate of Iron, probably made by passing 

 the iron hot through a solution of Silicate of Potash or some 

 such liquid. 



Dr. Cabot announced the donation of a specimen of 

 American Ostrich, Rhea Americana, from Col. Jacques, of 

 Charlestovvn, Mass. The thanks of the Society were voted 

 for the donation. 



January 19,' 1853. 



The President in the Chair. 



Prof. Rogers read the following memorandum on the 

 probable depth of the Ocean of the European chalk depo- 

 sits. 



Various geologists, and among them Prof. Ed. Forbes, in 

 his excellent and learned Palaeontology of the British Isles, in 

 Johnston's Physical Atlas, have suggested that the Ocean of the 

 Chalk deposits of Europe was a deep one ; and in evidence of 

 this, Prof. Forbes cites the " striking relationship existing to 

 deep-sea forms of the English Chalk Corals and Brachiopods, 

 adding that the peculiar Echinoderms, (Holaster, Galerites, 

 Ananchytes, Cidaris, Brissus, and Goniaster) favor this notion, 

 as also the presence of numerous Foraminifera. 



1 beg leave to present a difficulty in the way of this conclu- 

 sion. Several of these genera of Echinoderms, as Ananchytes^ 

 Cidaris^ Sf-c. occur in the Green Sand deposit of New Jersey, 

 referable by every fossil test to the age of the Green Sand and 

 Chalk of Europe. And this American stratum was unquestion- 

 ably the sediment of quite shallow littoral waters. That they 

 must have had a trivial depth is proved by the circumstance that 

 they repose in almost horizontal stratification, at a level of not 

 more than from one hundred to two hundred feet lower than the 

 general surface of the hills and upland region to the N. W. of 



