IV 



intended the execution of the lithography. The magnified 

 figures have in all cases been taken from nature, and for the 

 most part from specimens preserved in fluid, in order to 

 ensure a more natural aspect than that afforded hy dried 

 specimens. As they have been drawn with the aid of the 

 camera lucida, and to a scale which is given with each plate 

 or figure, the absolute and relative proportions of the dif- 

 ferent objects will be at once obvious. 



The other Parts will appear as soon as they can be pre- 

 pared. 



JOHN EDWARD GRAY. 



British Museum, 



August 1, 1852. 



