4 
97. Sp. Unio chloris , (Obliq. chloris. 
1828.) Shell oval obliqual, rather thick, and 
swelled; the 8 sides rounded, outside green- 
ish and smootb, inside bluish iridescent. 
Length 4-5, diameter 3-5, axis 1-5 of the 
breadth. 
Small streams of Knobhills. Minute shell, 
next to U. calendis Sp. 89, but distinct, la- 
mellar tooth more curved, and not bisulcate. 
Both are Sintoxia . 
98. Sp. Unio castaneus ; [Obliq. and Axi- 
media,1823.] Shell rather thin, oval, ellipti- 
cal, swelled, nearly equilateral, broader be- 
hind, outside very smooth, and chesnut co- 
lour; inside, bluish white. Length, 4-5; 
diameter, 3-5; axis 3-7 of the breadth. 
Knobhills streams, in east Kentucky.-— 
Very small, lamellar tooth suboblique, thin. 
Perhaps a variety of U. lenigata. Sp. 9. 
G. Truncilla. 
99. Sp. Unio perplexus. (Tr. perplexa, 
1830.) Shell rather suboval, slightly swell- 
ed, only subtruncate; rounded below, out- 
side olivaceous, with narrow black lines, in- 
side incarnate, iridescent. Length, 3-4, dia- 
meter, 1-3; axis, 2-5 of the breadth. Apex 
not prominent 
In the river Kentucky, about one inch, I 
have called it perplexing, because it devi- 
ates much from the other Truncilla , approx- 
imating to Scalenaria and Plagiola , but the 
hinge is like Truncilla. 
100. Sp. Unio granulatus, (Tr. granu- 
late, 1821. Shell thick, subtriedral, very 
much swelled, rounded below, posterior trun- 
cature nearly flat, subtesselate, granular; 
outside smooth, olivaceous, with broad black- 
ish bands, inside bluish white. Length 1-2, 
diameter 1-2, axis 1-3 of the breadth. Apex 
slightly cordate. 
In Salt river, rare, above one inch. Near- 
est to Tr. Triqueter , but less cordate, less 
tesselate, with granulations instead of warts 
behind. Not flexuose below, as Tr. truncate. 
Lamellar tooth very short. 
101. Sp. Unio metaplata. [Tr. do., 1822.] 
Shell thick, subtriedral, much swelled, broad 
and curved below, posterior truncature near- 
ly flat, hardly tesselate, subgranular above; 
cuticle yellowish, inside bluish white. Length 
3-4, diameter 5-8, axis 2-5 of the length. 
Apex deeply cordate. 
Var. 1. Vitiate , with black bands. 
In the Cumberland and Green Rivers, ve- 
ry rare; the largest Truncilla, often 2 inches, 
lamellar tooth crenulate, as in Tr. truncate. 
Sp. 19 
N. B. Besides these 26 new Unio, I find 
in my notes the account and figures of seve- 
ral others, such as U. pustulatus, U. puncta - 
tus , U. Scaber , U. elegans , U badius, U. cre- 
nulatus , &c. but not having now the speci- 
mens before me, I must delay their publica- 
tion. 
Of my previous species of 1820, but few 
are found in Lamark last edition of 1819. 
My U. latissima. is, perhaps, his U. recta. 
I found only 3 names, of different sp. from 
mine, clashing by similarity, U. retusa; U 
sinuate , and U. depressa. I have thus chang- 
ed mine in consequence. My U. retusa , 
1820, is now my U. premorsus; my U. de- 
pressa 1820, is my U. compressus; my U. si- 
nuate 1820 is my U. cultratus . 
Lamark and myself gave feminine termi- 
nations to our Unios; they are now generally 
made masculine, as I do here; but this dif- 
ference is of little account. 
The comparative proportions of the 
length, breadth, diameter, and axis of the 
Unios and other bivalve shells, having been 
misunderstood by some, it may be needful to 
state that my formula is a kind of abbrevia- 
tion of a longer exposition. Thus when I say, 
length one half , diameter one third, axis one 
fourth of the breadth— -l meant to say, and I 
must be understood to state the following 
longer account:— 
The length of the shell is one half , the dia- 
meter is one third, and the axis is at one 
fourth of the whole breadth, or largest di- 
mension of the shell. 
In longitudinal shells this is reversed, the 
length being the longest dimension, becomes 
the size of comparison. 
I ought 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 Masmodon 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 backwards in the sci- 
ence 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 sciences 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. 
II. Genus or tribe Alasmodon. 
This fine tribe of shells of which I knew 
only 2 species in 1819, was found rather pro- 
lific in species in 1820 and 1821. I ascer- 
tained then that it was also to be divided in- 
to several genera (subgenera or sections) of- 
fering many different peculiarities in the 
hinge. I have therefore established the fol- 
lowing 4 genera with it. 
1. Lasmigona. Cardinal tooth knobby, cre- 
nate and decurrent before. Lamellar tooth 
remplaced by an horizontal angular projec- 
tion, flat above. 
2. Amblasmodon. Cardinal tooth knobby 
erenate and decurrent before. Lamellar 
tooth remplaced by an obtuse oblique knob, 
a furrow between it and the ligament. 
3. Decurambis. Cardinal tooth bilobe 
flexuose enamelled, decurrent on both sides, 
decurrence remplacing the lamellar tooth be- 
hind, no angular knob to it. 
4. Sulcularia. Cardinal tooth small stri- 
ated decurrent before, separated by an 
