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XIX. — On the Minute Structure of the Calcareous Shells of some 

 Recent Species of Foraminifera. By W. C. Williamson, Esq., 

 Professor of Natural History in Owen's College, Manchester. 



(Read at the meetings of June 12 and June 26, 1850). 



Notwithstanding the large amount of attention that has been 

 given to the study of the Foraminifera within the last few years, 

 there is still very much of obscurity resting upon their history ; 

 wide differences of opinion existing both as to their true zoological 

 position, and as to the objects to be comprehended in the group of 

 animals so designated. 



As the Microscopical Society has honoured me by the publication 

 of my memoir on Polystomella crispa in their ' Transactions,' I have 

 been led to hope that the monograph has contributed in some 

 degree to the adoption of more accurate views as to the true nature 

 of these organisms, and I have hence been encouraged to perse- 

 vere in the inquiry. Accordingly I now lay before the Society 

 the results of some investigations into the structure of these 

 remarkable objects. It is my intention in the present memoir 

 to confine my remarks to some peculiar forms, chiefly belonging to 

 the three genera Amphistegina, Orbiculina and Nonionina, and to 

 describe the structure of their calcareous shells, which throw a con- 

 siderable amount of light upon those of Nummulina and Orbitoides, 

 to which so much attention has recently been paid by Dr. Carpen- 

 ter and Messrs. Jolie and Leymerie. 



Through the kindness of Mr. James Samuels, of Manchester, 

 recently a resident at Havannah, I have obtained some rich sand 

 from that locality ; sand, in the ordinary sense of the word, it is not, 

 being almost wholly composed of calcareous granules, Foraminifera, 

 spicula of sponges and Gorgonice, and abraded atoms derived from 

 the disintegration of shells, corals and echinoderms ; the whole 

 being really a modern limestone deposit in the first stage of its for- 

 mation. 



Amongst other beautiful forms of Foraminifera found in this Cu- 

 ban sand, are numerous specimens of the lenticular Amphistegina 

 gibbosa of D'Orbigny. When viewed under the microscope as an 

 opaque object, this species exhibits a smooth, white, glossy surface, 



TRANS. MIC. SOC. VOL. HI. P 



