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iii. 1843), he distinctly identifies each process of the soft animal, and 

 what he regards as the corresponding tube or oral (?) aperture in the 

 shell, with one individual animal ; each being separate from the nu- 

 merous others which he conceives are laid side by side with it r 

 throughout the several compartments. 



In our species, the articulation of the soft animal contained in each 

 chamber is one integral segment, to which other similar ones, occu- 

 pying the remaining chambers, are conjoined, combining to constitute 

 one perfect animal. These segments are connected together by one 

 row of necks in the very young state, and by several in the outer and 

 more developed portions. 



M. Ehrenberg considers that in his Geoponus, the tubes constitut- 

 ing both the outer and inner arches (fig. 5) are of the same nature ; 

 and that they alike perforate the septa, dividing the chambers from 

 one another, and that prolongations of the soft animal pass through all 

 these, forming necks, which intimately link together the soft contents 

 of adjoining compartments. 



In P. crispa, on the other hand, we have two classes of tubes, dif- 

 fering in their structure, and most probably in their function also. The 

 outer ones do not pass through the septa, but are separated from the 

 soft contents of the antecedent chamber by the calcareous film which 

 formed its anterior wall or boundary, previous to other chambers being 

 built up against it. Consequently the corresponding processes of the 

 soft animal (fig. 6, a and 7, c) are not tubular connecting necks, or 

 open channels of communication, but cul-de-sacs. 



Supposing M. Ehrenberg's drawings and observations to have been 

 accurately made, there is clearly a wide difference between his forms 

 of Polystomella, and those of which P. crispa is a type ; I have 

 now examined many from various parts of the globe, and have found 

 them all to assume the same general aspect and contour as that 

 already described, the modifications merely affecting the relative size 

 of the lateral processes, or the number of the connecting necks. 



In sea-sand obtained from various beaches, ranging from Torquay 

 to the Western Isles, as well as from the north-eastern corner of the 

 Mediterranean, there is found in some degree of abundance a small 

 but elegant Polystomella. The same species exists in considerable 

 quantities in the ancient deposit of foraminiferous sand, extending 

 under the fens of Norfolk and Cambridge. On mounting these in 

 Canada balsam, according to the method adopted by M. Ehrenberg, 

 I was at once struck with, the close resemblance of this widely 

 diffused species to his drawings of Geoponus stella-borealis. When 



