192 



observed by me have, I have no doubt, a secretion of carbonate of 

 lime in both valves equal to twenty times the weight of the included 

 soft parts of the animal. The secreting and depositing power here 

 is of an exceedingly large extent. 



These weights and measurements give us also the facts which de- 

 termine the power of development of the same species in different 

 localities, more or less favourable to vital energy, as adult specimens 

 are found in some places where their weight would not be one-tenth 

 of some of the specimens among those noted in the table. 



In a geological point of view, the facts are of some importance. 

 We find in the loamy deposits of the banks of some of the western 

 streams, large quantities of the existing species of the vicinity. 

 These beds are sometimes found to contain, at the height of eighty 

 feet above high water mark, the same species which exist in streams 

 cutting the neighbouring banks; and they must have lived there ages 

 before, ere the streams had cut their channels nearly so deep as they 

 are at present.* In all such cases, it would be well to note whether 

 any and what differences there may be between the same species re- 

 corded in the bluffs, and those still living in the stream below. 



The weights and measurements of the following species are taken 

 from specimens in my own cabinet, without the soft part of the ani- 

 mal being included. 











Diameter. 



Length. 



Breadth. 



No. 





Lbs. 



oz. 



Inches. 



Inches. 



Inches. 



1. 



Unio multiplicatus, 



2 



9i 



H 



5f 



8 



2. 



Unio crassidens, 





14 



^t\ 



4-2- 



5tV 



3. 



Unio crassus, 





IH 



9 9 



4 



5tV 



4. 



Margaritana complanata. 





10 



23 



6 



8 



5. 



Unio pustulosus. 





7 



9 s 





4 



6. 



Unio undulatus. 





64 



24 



3i 



4f 



7. 



Unio alalus. 





64 



2tV 



5 



H 



8. 



Margaritana undulata, 





54 



2A 



4tV 



7/0 



9. 



Unio tuberculatus, 





4§ 



H 



3/0 



74 



10. 



Unio verrucosus. 





2 



9 2 



44 



5 



11. 



Unio lacrymosus, 





1 



2t^^ 



4 



H 



12. 



Unio obliquus. 





154 



24 



3| 



^8 



13. 



Unio rectus. 





134 



2 



9 



"To 



14. 



Unio rubiginosus, 





8 



1 9 



h% 



4 3 



* I owe to Mr. Coleman Sellers the possession of several species found by 

 him near New Harmony, where they covered a space of half an acre, at the 

 height of eighty feet. 



