"8 RAFINESQUE’S 
and axis of the Unios and other bivalve shells, having been misunder- 
stood by some, it may be needful to state that my formula is a kind 
of abbreviation of a longer exposition. Thus when I say, length one 
half, diameter one third, axis one fourth of the breadth—I meant 
to say, and I sine be understood to state the following longer 
account :— 
The length of the shell is one half, the diameter is one third, 
and the axis is at one fourth of the whole breadth, or largest 
dimensions of the shell. 
In longitudirfal shells this is reversed, the length being the longest 
dimension, becomes the size of comparison. 
I onght to have added to the names of our late writers on Unio, 
Mr. Hildreth, who.has described over again a few of my species, and 
Prof. Eaton, who I regret to say, has, (in his Zoological, Text- 
Book, Albany, 1826, now before me,) noticed 33 species of Unio and 
Alasmodon of Say and Barnes, but none of my previous ones! and 
put them all back to the old genus Mya of Linneus! This, as well 
as his whole Zoological book, proves that he is forty years back- 
wards in the science of Zoology, as he is 30 years backwards in 
Botany, and about 20 in Geology. But this is not peculiar to him, 
it is the fate of one half of our Naturalists, Botanists and Geologists. 
The daily increase of knowledge and improvement in science is 
despised or neglected by them as useless innovations! While all the 
world, and all the sciences move forward, they would keep those 
they teach or cultivate at a stand! it is all in vain, and time will 
show it. 
P i} 
II. Genus or tribe ALASMODON. 
This fine tribe of shells of which I knew only 2 species in 1819, 
was found rather prolific in species in 1820 and 1821. I ascertained 
then that it was also to be divided into several genera (subgenera 
or sections) offering many different peculiarities in the hinge. I 
have therefore established the following 4 genera with it. 
1. Lasmicona. Cardinal tooth knobby, crenate and decurrent 
before. Lamellar tooth remplaced by an horizontal angular pro- 
jection, flat above. 
2. AMBLASMODON. Cardinal tooth knobby, crenate and decurrent 
before. Lamellar tooth remplaced by an obtuse oblique knob, a 
furrow between it and the ligament. 
