1 hs 
THE - CONCHOLOGISTS’ - EXCHANGE. 
21 
or white. Beaks not prominent, with very 
slight undulations ; and having the calcareous 
and ferruginous deposits covering the entire 
margin of the shell. A second variety also 
occurs in our creeks, differing quite materially 
from the variety just described. It is oblong- 
oval in outline; solid; beaks prominent with 
much heavier undulations. Epidermis varying 
from dark olive to light brown. In the left 
valve of this variety there is a short, but well 
defined, cardinal tooth with a notch in it fitting 
into the deep cleft in the primary tooth of the 
right valve. In fact, many individuals of this 
variety, owing to the teeth, might be mistaken 
for specimens of Margaritana. This variety 
varies much in respect to its rays; many being 
rayless, others covered with beautiful rays, 
sometimes capillary. It is, when adult, quite 
angular over the umbones. The third variety 
is found in the river only, and in some respects 
resembles Anodonta ferruginea, Lea, from In- 
diana. It is a thick and solid variety, with a 
dark brown epidermis. The nacre is either 
rose color or a light salmon, with a dark pink 
border around the margin of the shell. Beaks 
prominent, incurved, with undulations large and 
coarse. Rays dull, often obsolete. Animal 
often red, sometimes salmon color. ‘This spe- 
cies is usually found where the current is quite 
strong, on sandy or gravelly bottoms. 
52.—Anodonta imbecilis, Say. 
This fine species has a geographical distribu- 
tion from New York to Texas, and throughout 
this wide range varies but little. It is asmooth 
shell, oval in outline, cylindrical, slightly in- 
flated, and very thin, yet it keeps well in the 
cabinet. It usually has a brilliant green epi- 
dermis, often marked with concentric green 
bands, sometimes with alternating bands of a 
darker shade of green or dark olive color. 
Beaks very minute, scarcely visible and covered 
with very minute undulations. Nacre shining 
and bluish white; when young a yast number 
of very narrow, faint rays are often observable. 
This shell is found here only in the sloughs of 
the river, in the small iakes of the *Bay Island 
always where there is a soft, muddy bottom, 
*This island has been incorrectly styled ‘ Bog Is- 
i} land ’’ in former descriptions.-—-Epiror, 
and is very abundant. ‘There is one mystery 
about this shell that I have never been able to 
solve, and that is that of the many thousands 
that I have seen and collected I never found 
one fully grown. What becomes of them I do 
not khow. I have received very fine adult 
specimens from many of my correspondents 
from difterent localities, but all my efforts to 
obtain an adult specimen from Mercer County, 
have been in vain. This species is very pro- 
lific, producing its young in incredible numbers, 
of which fully one-half die from some unknown 
cause when not over one-fourth grown. 
53--—Anodonta grandis, Say. 
Shell smooth, oval and inflated. Beaks 
rounded, very prominent and slightly incurved. 
Undulations on beaks quite large, zig-zag in 
shape and varying from six to eight on each 
valve. Epidermis varying from dark brown to 
light olive, and often found with greenish streaks 
running transversely. The nacre varies from 
dull salmon through light pink to dull white. 
Cicatrices large and plainly observable when 
not covered with mineral deposits. Gvazdzs is 
the type of a number of very interesting al- 
though very closely allied species, the most pro- 
minent of which are plana, decora, ovata, and 
corpulenta. ‘Typical forms of these species are 
easily separated when once well known, lgut 
intermediate forms are so extremely puzzling 
that no conchologist can separate them to a 
certainty. 4. grandis is found rather common 
from Ohio to Texas, and varies wonderfully in 
different localities. It is reported very common 
in many portions of Illinois, but it is a singular 
fact that not over half a dozen specimens have 
been found in Mercer County. Our specimens 
are far from typical and are close to corpz/enta. 
It is found here only in the river sloughs asso- 
ciated with corpulenta aad zmbecilis. It differs 
from corfulenta in being smaller, less inflated, 
and in haying the beaks more rounded and 
heavier. The color of the shell over the sum- 
mit is always of a lighter shade, and it never 
has the copper colored nacre of corpulenta. 
Adult forms of grandis are much more solid 
with very much more prominent growth lines 
than corpulenta. 
To be Continued. 
