358 ANNALS OF THE CARNEGIE MUSEUM. 
Truncilla rangiana (Lea). 
Six males, four sterile and four gravid females, from the upper 
Allegheny River drainage in Pennsylvania, are at hand. 
The gravid females, with eggs and glochidia, were found in 
September. 
This form is generally regarded as a variety of T. perplexa, but Walker 
(1910c) separates it as a species. All specimens examined by me are 
true rangiana, but they do not agree with the characters given in 
Walker’s key (J. c., p. 80), since the color and texture of the marsupial 
expansion is, in old females, quite different from the rest of the shell, 
being horny and lacking in lime. In young females, this is not the 
case. 
As to the soft parts, see Ortmann (19110, p. 322), and also those of 
perplexa, described by Lea (Obs., X, 1863, p. 420). 
Fic. 28. Truncilla rangiana (Lea). Gravid female, from French Creek, Cochran- 
ton, Crawford Co., Pa. (Carn. Mus., No. 61, 3,363.) Coll. Sept. 2, 1908. 
Anal, supra-anal, palpi, structure of gills, and marsupium generally 
asin T. triquetra. The marsupium is greatly swollen, rather low and 
long, notso much deformed. Glochidia (figured as of perplexa by Lea, 
Obs., VI, 1858, pl. 5, fig. 21) are also similar; length 0.26; height 
0.23 mm., but my measurements are not very accurate, since all the 
glochidia I have are very young and delicate. 
In the female, the two edges of the mantle diverge greatly in front 
of the branchial, the outer one curving outward, and forming a great, 
almost semicircular lobe, with a smooth edge; while the inner one runs 
almost straight downward and forward; the two edges coming together 
