74 
BRIEF NOTES ON THE LAND AND 
FRESH-WATER SHELLS OF 
MERCER CoO., ILL. 
BY WILLIAM A. MARSH. 
(Continued.) 
34.-—Unio rubiginosus, Lea, 
A very variable species which inhabits Pope 
and Edwards Creeks. I have never found it 
in the river. It varies much in outline. Sex- 
ual differences are quite marked; the females 
being more inflated and slightly emarginate. It 
has a dark brown or rubiginose epidermis 
sometimes of a greenish or yellow tinge, vel- 
vety in texture, and usually has a white nacre, 
often shining and iridescent. Some have a 
very pale rose-colored nacre, while others are 
of alight salmon color. ‘This abundant and 
widely distributed species often bears strong 
resemblance to a number of both northern and 
southern described forms. It is often found 
associated with both coccéneus and trigonus 
and is then difficult to separate from them 
unless the collector familiarizes himself with 
the specific differences of the three forms. It 
differs from ¢v7gorus in being more depressed, 
more elongated, more rounded over the um- 
bones, in having lighter cardinal and_ lateral 
teeth and very much éess prominent growth 
lines. Its beaks are less ponderous and the 
undulations also quite different. It differs herve 
from cocctneus in having a darker and rougher 
epidermis, in the undulations of its beaks, in 
its teeth, and general outline and color of its 
nacre. In our creeks it is an active species 
and is found in all kinds of situations; on the 
sandy bars, in the gravel, under the projecting 
edges of large rocks, in water very highly 
impregnated with iron ore, in the mud, and 
even under logs submerged in the water. 
Unio solidus, Lea. 
Ss 
An inhabitant of the deep water of the 
Mississippi River. This is a rare shell and I 
THE) CONCHOLOGISTS?- 
EXCHANGE 
. 
consider it extraordinary good luck to find 
three or four specimens in a season. As _ its 
name implies it is a thick, solid shell, epider- 
mis dark reddish brown, growth lines smooth, 
beaks smooth and massive and slightly incury- 
ed, rays dark green or dark brown. It isa 
very distinct species, yet, judging from the 
many names I have received it under from 
collectors, it is not well understood. Of our 
local species, it most resembles “7gonus. The 
Unio plenus and the cati/lus, of Conrad, are 
often mistaken for this shell, but its green or 
brown rays, rounded umbones and massive 
beaks will, however, always distinguish it from 
those forms. The color of the interior varies” 
from white and light rose to a beautiful pink 
and even salmon color. 
36.— Unio spatulatus, Lea. 
This species is found only in Pope and_ 
Edwards Creeks and never in the river. It 
was once very abundant here but, owing to- 
the constant ravages of hogs, coons and musk- 
rats, it is now nearly extinct. It is a finely 
shell, covered with dark-green rays, slightly 
undulate, and in this character it much resem-— 
bles gamentinus with which it groups. Its” 
cardinal teeth are small, and when found in 
iron ore water they are always stained with 
that substance. The animal seems to prefer 
gravelly situations, and very frequently buries_ 
itself so deeply in sand or gravel that it is 
difficult to find. 
37-—Untio subovatius, Lea. 
This species is found very sparingly in Pope 
and Edwards Creeks. It is the male of Unzo 
occtdens, Lea, and in many respects is strik- 
ingly similar to verdricosus, Barnes. It often 
attains an immense size and is provided with 
very large beaks and teeth. Its surface orna- 
mentation is extremely variable, for while 
some specimens are provided with beautiful 
green rays, varying greatly in width, others are 
found with a few dull rays over the anterior 
portion of the shell, while others still are en- 
tirely devoid of rays. 
