1878. ] Zoölogy. 391 
This shell is held by Mr. Binney, if I mistake not, to rank only 
as a variety of the Æ. diodonta Say. In this Mr. Binney is follow- 
ing, no doubt, closely in the line of recent zodlogical testimony; 
but if this species is to be held as a synonym, it will be difficult 
to convince any fair-minded student of our shells, that, under the 
same law of interpretation, Æ. mayor Binney, is not a synonym of 
F. albolabris Say, as held by Mr. Bland; or that Zonites subplanus 
Binney, is other than a variety of Z. inornatus Say ; or Z. capnodes 
Binney, anything but a variety of Z. fuliginosus Griffith. A 
“general resemblance ” in the “jaws” and “linguals” of certain 
groups, so vague as to render the expression “jaw as usual in the 
group ” sufficiently definite, makes a very convenient post about 
which to lash the whip of synonyms; but there are other charac- 
ters, which only the collector can know, that ought, it seems to 
us, to be taken notice of in all our accounts with authors who 
have written upon species. 
The writer first found the large variety of H. diodonta several 
years ago in Whitley County, Kentucky. He has since collected . 
it in numerous localities of the Carboniferous sandstone region of 
South-eastern Kentucky and Northern Tennessee, and it has 
never failed, in a single specimen, to exhibit its normal characters, 
Save in the single particular of size. While shells have been 
found nearly double the dimensions of Maine specimens received 
from Mr. Allen, and nearly treble those of New York examples 
from Dr. Lewis, none have ever been seen, at all approaching, in 
this particular, the smallest specimens of Æ. chilhoweénsis. The 
latter shell has nearly one whorl more than the H. diodonta ; it 
has no tooth on the lower third of the peristome, and at least 
one-half the specimens which I have collected want the parietal 
tooth. My largest specimen measures 39 mill. in diameter and 
20 mill. in height. There is very little variation in the size of 
the specimens which I have seen. The animal is slender, quite 
sluggish in movement, and not timid as is the case with Z. diodonta. 
The surface is roughened with irregular, reniform tubercles, the 
tentacles are very long and delicate, and the foot attenuate and 
keeled posteriorly. : 
It has a habit of greatly flattening and spreading its foot, 
especially after full-feeding, and will in that condition, remain for 
ours upon smooth surfaces of planed boards, pebbles or lettuce- 
leaves, evidently in calm enjoyment of its meal, having, in this 
respect, the exact habit of the European Æ. pomata L. in- 
habits the dense thickets and Kalmia jungles of the Jellicoes, and 
is rare, even in its native habitat. 
The great size of this shell, and that of other species of wider 
range found with it, offers an argument controverting the prevail- 
ng opinion that limestone regions only are favorable to molluscan 
ifi ; 
e. r 
These shells are found in the carboniferous sandstone mountains 
