Ortmann: Families and Genera oi Najades. 297 



on the margin anteriorly, into white posteriorly. Edge of mantle 

 brown, posteriorly orange, mottled with Mack spots. Adductors 

 grayish to orange. The orange tints arc 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, pi. 5, fig. 27) rather large, higher 

 than long, with hooks. Length 0.33; height 0.36 mm. 



Color entirely like that of .1. 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 Lastexa Rafinesque. (1820.) 

 (Simpson, 19006, 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 



