NATURAL SCIENCES OF PHILADELPHIA. 143 



times yellow. Structure fine granular, approaching micaceous. Hardness 

 2—2-5 S. G. 2-05. B. B. alone blackens slightly and fuses rather easily to 

 a white slag. With carb. soda fuses readily and with effervescence to a green- 

 ish bead. In borax dissolves readily iron reaction. In microcosmic salt dis- 

 solves readily, except silica skeleton, bead yellow while hot, bluish opalescent 

 when cold. In closed tube yields acid water. 



With considerable difficulty 0-679 gm. of the mineral, free from admixture, 

 was obtained and submitted to analysis with the following percentage result : 



Water 3-42 



Fluorine -75 



Silica 36-49 



Sesquioxide of iron 7-54 



Alumina 24-09 



Soda 16-03 



Loss 11-68 



100-00 

 The very small quantitj' of the mineral which could be procured prevented 

 a more satisfactory result, but from the foregoing characteristics 1 feel justi- 

 fied in pronouncing it a new species, and hope that a larger quantity may be 

 procured and a correct analysis made. 



Pachnolite, besides its usual occurrence in honey-combed cryolite, nearly 

 or always in juxtaposition with the so-called Hagemannite, has been observed 

 in crystals implanted on massive cryolite, and also coating crystals of the 

 latter, mix'-d with microscopic crystals of cryolite. The crystals of pachno- 

 lite are always small, rarely exceeding the fiftieth of an inch in diameter, but 

 those of cryolite have been found measuring over 3-lOths of an inch cube. The 

 crystals of carbonate of iron, found in the cryolite, have probably never been 

 excelled for size and beauty. They are usually simple rhombohedrons, often 

 of fine polish and measuring from half an inch to four inches across. A 

 black blende, containing much iron, has been found in the massive cryolite, 

 crystallized in perfect octahedra. 

 Philadelphia, March 23, 1868. 



Doicription of Sixteen New Species of the Genus TJNIO of the United States . 

 BY ISAAC LEA. 



Un'io Murrayexsis. — Testa laevi, obliqua, tumida, solida, valde inaequila- 

 terali, postice rotundata, antice truncata; valvulis crassis, antice crassiori- 

 bus ; natibus valde elevatis, tumidis ; epidermide luteo-fuscata, concentrico- 

 vittata, eradiata ; dentibus cardinalibus crassis, subelevalis; lateralibus 

 crassis, obliquis rectisque ; margarita argentea et iridescente. 



ff/b. — Murray County, Georgia, Maj. T. C. Downie ; Etowah River, Georgia, 

 Bishop Elliott. 



Unio fassinans. — Testa l;evi, elliptica, subcompressa, inaequilaterali, pos- 

 tice obtuse angulata, antice rotundata; valvulis crassiusculis, autice crassi- 

 oribus ; natibus subpromiuentibus ; epidermide teuebroso-rufo-fusca, eradi- 

 ata; dentibus cardinalibus crassiusculis, compressis, obliquis; lateralibus 

 sublongis, crassis, obliquis corrugatisque ; margarita salmonis colore tiucta, 

 splendida et iridescente. 



Hab. — Headwaters of Holston River, Washington Co., Va., Prof. E. D. Cope. 



Unio spards. — Testa lajvi, lato-elliptica, subinflata, valde infequilaterali, 

 postice obtuse angulata, antice rotundata ; valvulis subtenuibus, antice cras- 

 sioribus ; natibus prominulis, ad apices minute undulatis ; epidermide sub- 

 crocea, valde radiata ; dentibus cardinalibus parvis, erectis, conicis ; laterali- 



1868.] 



