466 



Mr. G. B. Sowrrdv's Remarks 



proper situation in the natural system of the shell described by 

 Montagu under the name of Patella distorta, Linn. Trans, xi. 

 p. 195. t. 13. f. 5. 



The first specimen I had ever seen of the genus Orbicula was 

 sent to my father some months ago by Mr. Holloway, from 

 Portsmouth ; it was found by him precisely under the same cir- 

 cumstances as those under which I have myself obtained speci- 

 mens : but this specimen was so very much distorted, and withal 

 so new in its appearance, that it was impossible to form an opi- 

 nion upon it. 



The next specimen of this genus that it has fallen to my lot to 

 examine, was in the possession of Mr. Mawe, from whom I 

 am informed it has passed into Lady Wilson's cabinet : this is 

 another species, very much resembling, if it be not, Orbicula 

 norvegica ; it is larger than any of the former, and was attached 

 to the convex outside of a grey flint pebble, and not defended 

 by a cavity in the stone. The dried animal remains within, by 

 which we are enabled to show that it belongs to the family of 

 terebratuloid shells, the Branchiopoda of Cuvier. 



The discovery above mentioned, of a number of specimens of 

 the genus, has led to a more intimate acquaintance with its cha- 

 racters and habits ; and as the means are thus offered to our use, 

 it may not be improper to give an amended generic character, 

 and such additional information concerning the genus as I have 

 been able to collect from the specimens themselves. 



ORBICULA. 



Bivalve, inequivalve, nearly orbicular, compressed, fixed ; up- 

 per valve patelliform, with four internal muscular impres- 

 sions, two rather large and approximating near the centre, 

 and two smaller and more distant placed near the posterior 

 Lower valve flat, with corresponding muscular im- 

 pressions 



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