300 Annals of the Carnegie Museum 



been found on April 22 and 24, and May 6 and 11. The latest date 

 for gravid females in spring is May 22. 33 



Lea (Obs., II, 1838, pi. 15, fig. 47) has published a very poor figure 

 of the soft parts, and descriptions of the latter (Obs., X, 1863, pp. 450 

 and 453). 



Mantle-connection rather short, shorter than the anal. Inner edge 

 of anal crenulated, that of branchial papillose. Posterior margins of 

 palpi connected at base only. 



Diaphragm normal. Inner lamina of inner gills very variable. In 

 most cases it is connected anteriorly for about one-half of the length of 

 the abdominal sac, in other cases the connection is much longer, and 

 not unfrequently the inner lamina is entirely connected. Anterior 

 end of inner gill about halfway between that of the outer gill and the 

 palpi. Septa of the gills distant from each other in the male and the 

 non-marsupial gills of the female. The outer gill alone is marsupial, 

 with much more crowded septa. When gravid, the gills swell greatly, 

 distend at the edges, and lateral water-canals are formed. In addition, 

 the ovisacs are divided into compartments as described above. Pla- 

 centulae containing two to ten (or more) ova or glochidia. The 

 placentulae and glochidia have been figured by Lea (VI, 1858, 

 pi. 5, figs. 37 and 38). The latter are not very large, subtriangular, 

 longer than high, and have hooks. Length 0.36; height 0.30 mm. 



Color of soft parts quite variable, but with the same tendency as 

 Alasmidonta undulata to have certain parts (foot, edge of mantle, and 

 adductors) orange. Some specimens (chiefly young ones) are more or 

 less uniformly grayish or yellowish white, while others exhibit all 

 shades from yellowish through brownish orange to bright orange. 

 Gills mostly paler or darker brown, shading to orange. Mantle edge 

 blackish, with the same orange and black spots as Alasmidonta un- 

 dulata. Marsupium, according to contents, pale yellow, or creamy, 

 to brown. 



Subfamily LAMPSILINjE. 

 A large number of forms belong here, which, as far as we know, are 

 all found in North America, extending southward into Central America. 

 Indeed, Simpson associates with these a number of Asiatic and African 



33 According to Lefevre and Curtis (191 1) the "interim" is in July in Wisconsin, 

 probably corresponding to the higher latitude. In 191 1 I found gravid and dis- 

 charging females in West Virginia on May 11, 12, and 13, but on May 23, 24, and 25 

 no gravid females were any more seen. 



