Ortmann; Families and Genera oi Najades. 269 



Color of soft parts of ]■'.. beadleianus whitish; fool grayish; gill 

 palpi grayish-brown, as is also the mantle, except the margin, which is 

 whitish, with the edge blackish posteriorly. 



Elliptio (?) spinosus (Lea). 

 The anatomy has been described by Lea (Obs., X, 1863, p. 413). 

 li is similar to thai ol E. crassidens, bul Lea mentions some peculiar- 

 ities in the ovisacs, which I do not understand. The shell is of the 

 crassidens-type, but its spines are unique and would possibly justify 

 the erection of a separate genus: Canthyria Swainson, 1S40. 



Elliptio complanatus (Dillwyn). 



Numerous specimens of this species, males, sterile and gravid 

 females, have been investigated from the Delaware, Susquehanna, and 

 Potomac drainages of eastern Pennsylvania and Maryland. The 

 species is tachytictic, and the breeding season begins at the end of 

 April, and lasts to the middle of June, possibly a little longer. 



The soft parts have been described by Lea (Obs., X, 1863, p. 



41-')- 



In the shell, this is a typical Elliptio, with the typical shape of this 

 genus, and its typical beak-sculpture. In the soft parts, we find the 

 edges of the mantle forming the usual openings. Anal and supra-anal 

 are separated by a moderate mantle-connection, shorter than the anal, 

 which has never been found missing. The branchial has large papilla;, 

 while the anal has much finer ones. Posterior margins of palpi con- 

 nected for a short distance. 



Gills corresponding to the shape of the shell, rather long and 

 moderately wide, the inner rather wider. Diaphragm of the usual 

 shape, inner lamina of inner gill free, except at anterior end. Septa 

 and water-tubes well developed, the latter wide in the male. In the 

 female only the outer gills are marsupial, and their septa arc much 

 crowded. When gravid, this gill swells only moderately, the edge 

 remaining sharp, and the ovisacs assume a leaf-like shape, as also do 

 the placenta; (figured by Lillie, 1895, pi. 1, fig. 1), which are not very 

 solid when glochidia are present. The latter are always white,, 

 rather small, subovate, without hooks. They are longer than high. 

 Length 0.20, height 0.19 mm. (see Plate XIX, fig. 1). 



Color of soft parts of the grayish white type, foot darker, also gills, 

 the latter often suffused with black posteriorly. 



