9 
occurs there. How many more of the western spe- 
cies inhabit the Atlantic rivers of East Florida, is an 
interesting problem which some future observer 
must solve. 
The propriety of separating the Naiades into so 
great a number of species, especially as they have 
been divided by RarFinesqueE and Lea, has often been 
doubted by conchologists.. In general, however, 
they are sufficiently defined, although Mr. Lea has 
imposed new names of his own upon species long 
before described by others, evidently wishing to be 
considered sale authority in this branch of Concholo- 
gy. Few, however, will be willing to take his zpse 
dizit for the justice of his claims. 
Colour of the nacre. This has been supposed to 
be characteristic of certain species, which, it is said, 
never vary materially in the colour of the interior, 
Thus, Unio ater, Lea, U. torsus, Rar. and some 
others are invariably purple or rose coloured; but in 
others again, the nacre varies from pure white to 
every shade of salmon, rose colour, pink and purple. 
The *Unio nasutus, of Say, is a good example of 
* Mr. Lea observes that the U. nasutus ig “either white 
or approaching salmon colour under the beaks.” I many 
. b] 
h 

