104 THE - CONCHOLOGISTS’ - EXCHANGE. 
common Limnzea, being found along the margins 
of all our small Jakes and Mississippi River | 
bottom ponds, also in all ponds along 
our small creeks, especially about springy 
places, and in grassy marshes. One remarkable 
feature however is noticeable: that the species 
attains a much larger size in the ponds of the 
river bottom than it does in the inland ponds, 
but is the same in other respects. This species 
puts in an appearance much earlier in the 
Spring than the other Limnzas. In the early 
part of May it may be collected in vast num- 
bers about springy places, usually from very 
small to about half-grown. It can then be 
found crawling around over the moist ground 
some distance from the water. 
89.—Limnea zebra, Vryon. 
Shell turrited, thin; spire very attenuate; 
whirls from six to seven, brownish yellow, 
translucent, irregularly striate, covered with 
whitish transverse lines or stripes, imperforate; 
sutures impressed ; aperture narrow, elliptical. 
It usually has from one to three obscure brown 
lines within the margin of the outer lip. This 
very beautiful species is found in small ponds 
along Pope creek, and in the Doak Swamp, in 
the Mississippi River bottom, “In the latter 
locality associated with Lzmnca reflexa Say.” 
It generally begins to put in an appearence 
about the first of May, and disappears about 
the latter part of June. I have taken very 
young specimens of this shell and put them in 
an aquarium with //anorbis, Physa, etc. In 
this condition they grow very much more solid, 
but attain their growth in a dwarfed condition, 
not more than half their natural size, and with- 
out the pale whitish stripes, which always 
characterize the species in its normal condition. 
go.—Limnea caperata, Say. 
Shell somewhat oval, slightly oblong, light 
horn color; whirls six; apex acute, covered 
with numerous minute revolving lines; sutures 
not very deeply impressed; aperture large, fold 
of the labium not prominent. ‘This fine shell 
is very rare here. Seven specimens before me, 
found on the Bay Island, in 1877, is all that I 
know to a certainty as ever being found in the 
county. I know nothing of the habits of this 
shell. It is probably common in the northern 
portion of the State. A number of years ago I 
received a large lot of this fine shell, collected 
by Mr. H. A. Pilsbry, in Iowa. 
To be Continued. 
NOTES ON THE UNIONIDA. OF 
FLORIDA. 
BY DR. S. HART WRIGHT & BERLIN H, WRIGHT. 
In Conchology, and especially in the Unioni- 
dee, it is very often difficult to separate distinct 
species of the same group. ‘This is owing to 
the very few distinct specific characters which 
shells have. In the Unionidz there appears to 
be a character in the ratio of the altitude (length 
from base to dorsum) to the transverse or longi- 
tudinal axis, which we will represent by “ R,” 
in our notes. In individuals of the same spe- 
cies, if not very young, “ R” is substantially 
constant. In co-related species, or in specimens 
that appear to be the same, if on finding “ R” 
to be clearly of a different value, the assumption 
may be taken that the species or specimens are 
not the same. 
The location of the tip of the beaks, and 
(when well formed) of the cardinal teeth, is 
also a character, and in specimens of the same 
species having nearly the same size or age, is 
substantially constant. The location of these 
joints from the anterior end is readily compared, 
in two individuals supposed to be alike or un- 
like, by taking the left valves of each, placing 
the anterior ends of each against the table or 
desk, one being horizontal and the inside facing 
upwards, and the other placed upon it, verti- 
cally and dorsum downward, will easily show 
the agreement or non-agreement of the location 
of the beaks and cardinal teeth. The signifi- 
cance of the specific names of species, we will 
» 99 
give and the value of “ R. 
