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PROCEEDINGS OF THE ACADEMY OP 
Above, including the entire upper surface of the wings and scapulars, bright 
grayish ash, the inter-scapular region reddish chestnut-brown. Beneath ashy 
white, the middle of the belly almost pure white. Lores abruptly black. Quills 
and tail feathers nearly black ; two outer entirely white ; the third with brown 
on the inner edge. Length 6-25 ; wing 3-05 ; tail 3-10 inch. 
Hah. Fort Thorn, New Mexico. 
This species differs from Junco cinereus, {Fringilla cinerea, Sw.) in the absence 
of chestnut-brown on the wing coverts and tertials. 
Description of Four New Fresh-water Molluscs, from the Isthmus of Darien and 
Honduras. 
BY ISAAC LEA. 
Unio Caldwellii. Testa sulcata, elliptica, subinflata, postice obtuse angulata, 
inaequilaterali ; valvulis subcrassis ; natibus subelevatis, ad apices minute un- 
dulatis ; epidermide luteo-fusca ; dentibus cardinalibus compressis, elevatis 
crenulatisque ; lateralibus sublongis subrectisque ; margarita salmonis colore 
tincta et iridescente. 
Zfa&.— Isthmus of Darien. H. C. Caldwell, M. D., U. S. Navy. 
Unio Gtoascoranensis. Testsi Isevi, elliptica, subcompressa, postice obtuse 
angulata, valde inaequilaterali ; valvulis subcrassis, antice crassioribus ; nati- 
bus prominulis ; epidermide fuscescente, transverse striata ; dentibus cardi- 
nalibus parviusculis, suberectis crenulatisque ; lateralibus sublongis subrec- 
tisque ; margarita alba et iridescente. 
Hah. — River Groascoran, Honduras, Pacific Slope. J. L. LeConte, M. D. 
Anodonta luteola. Testa laevi, obovata, subcompressa postice et antice 
rotundata, inaequilaterali ; valvulis subtenuibus ; natibus prominulis ; epider- 
mide luteo-oliva, transversim striata ; margarita alba et valde iridescente. 
i7a6.— Isthmus of Darien. H. C. Caldwell, M. D., U. S. Navy. 
Melania planensis. Testa Isevi, subfusiformi, magna, crass^, tenebrosc- 
fusca ; obsolete maculata ; spira elevata, conoidea ; suturis paulisper impressis ; 
anfractibus instar novem, conv^iusculis, striis transversis exilissimis impres- 
sis ; apertura grandi, ovata, s\iperne angulata, intus fuscata ; labro acuto ; 
columella albida, superne inspissata. 
Operculo tenebroso-fusco. 
Hah. — Plan and Omoa, Vadley of Ulua River, Atlantic slope, Honduras. 
J. L. LeConte, M. D. 
Memoranda of the eflPects of Carburetted Hydrogen Gas upon a collection of 
exotic Plants. 
BY GE#RGE W. FAHNESTOCK. 
During tbe prevalence of severe cold weather in the latter part of January, 
and first few days in February, 1857, the earth was frozen to an unusual depth. 
Beneath the stone pavements in the streets of Philadelphia, the frost penetrated 
to a depth of more than three feet. In the neighborhood of Arch and Eighteenth 
streets, and along both, those streets for the distance of nearly one hundred 
yards, the escape of gas from the main pipes under the street had been re- 
marked for several weeks. Leaks at the joints had probably existed for months, 
although, the porous nature of the soil had allowed the gas to diffuse itself, and 
find numerous vents at the surface. But the solid crust of frozen earth forced 
it to seek other channels of escape. 
At this time, with the thermometer ranging from zero to 10'' or 15^ Fahren- 
heit, a current of gas, penetrating the imperfectly secured joints of the main 
[May. 
