ORTMANN: FAMILIES AND GENERA OF NAJADES. 297 
on the margin anteriorly, into white posteriorly. Edge of mantle 
brown, posteriorly orange, mottled with black spots. Adductors 
grayish to orange. The orange tints are often rather pale, inclining 
toward grayish yellow. Marsupium charged with eggs pale yellow; 
with glochidia brownish. 
Alasmidonta marginata (Say). 
Of this species, and of its eastern variety varicosa (Lamarck) a 
large number of specimens have been investigated, both from the 
Ohio and the Atlantic drainages in Pennsylvania. 
Bradytictic, breeding season beginning in August, and lasting until 
May. Discharging specimens have been found on May 3. 
The anatomy has been discussed by Lea (Obs., X, 1863, p. 446) and 
Simpson (in Baker, 1898, p. 63). 
Soft parts essentially like those of A. undulata, to which species it is 
indeed closely allied. The mantle-connection between anal and supra- 
anal is much shorter. I have found the inner lamina of the inner gills 
always connected with the abdominal sac, although Lea (/. c.) says 
that it is sometimes more or less free at the posterior end. Posterior 
margins of palpi connected at base only. 
Glochidia (see Lea, Obs., VI, 1858, pl. 5, fig. 27) rather large, higher 
than long, with hooks. Length 0.33; height 0.36 mm. 
Color entirely like that of A. undulata, with a strong tendency 
toward orange tints; posterior margin of the mantle spotted with black 
and orange. Marsupium, according to contents, yellowish white to 
brown. 
Genus LASTENA Rafinesque. (1820.) 
(Simpson, 1900), p. 654.) 
Shell elongated; not inflated; without distinct posterior ridge. Disk 
smooth. Beak-sculpture concentric, bars irregular, coarse, middle 
part nearly straight. Hinge with rudimentary teeth, pseudocardinals 
only vestigial, laterals absent. 
Soft parts only of male and sterile female known, but as far as can 
be seen anodontine in structure. Inner lamina of inner gills free. 
Mantle-connection between anal and supra-anal rather short. 
Type L. lata (Rafinesque). 
According to the characters of the shell, this genus stands between 
