Ortmann; Families and Genera of Najadi 247 



eason lasts from the middle of Ma\ to the middle ol |ulv. The 

 discharge of the glochidia has been observed on July 8, 1909. 



The sofl parts have been described by Lea (Obs., X. 1863, p, 417), 

 but incorrectly in several particulars. They also have been described 

 by Simpson (in Baker, 1898, p. s jK 



Margin of the mantle drawn together by the gill-diaphragm, thus 

 separating the anal and branchial openings. Anal and supra-anal 

 separated by a very short mantle-connection, which is sometimes absent 

 I torn?). Branchial opening with strong papillae, anal also with papillae, 

 which, however, arc much finer, and sometimes appear only as crenu- 

 lations. Palpi of the usual shape, their posterior margins connected 

 only at base or up to one-third of the length. 



Gills broad, the inner the wider, their anterior ends as usual. Dia- 

 phragm normal, and inner lamina of the inner gills free from the ab- 

 dominal sac, except at the anterior end. 



Gills with well-developed septa and water-tubes, as usual. In the 

 female, marsupial structure is observed in all four gills, the septa being 

 better developed, with folded epithelium, closer together, and the 

 water-tubes being narrower. Yet in theoutergill the water-tubes are 

 somewhat narrower than in the inner gill, which is chiefly noticeable 

 at the base oi the gills. In the gravid female, the gills swell moder- 

 ately, so that the ovisacs assume a lanceolate, leaf-like shape, while the 

 edges of the gills remain sharp and do not distend. Eggs whitish, 

 tilling the ovisacs in rather poorly connected masses, although a pla- 

 centa-like cohesion is seen. But later on this placenta-structure is 

 lost, and the glochidia are discharged in rather loose, irregular masses. 



Glochidia of suboval shape, without hooks. Length 0.21; height 

 0.22 mm. (see Lea, Obs., VI, 1858, pi. 5, fig. 22, but not quite correct 

 in shape; Ortmann, 191 \h, pi. 89, fig. 3). 



Color of soft parts whitish, foot, margin of mantle and gills pale 

 brownish or yellowish. No trace of any brilliant colors (red or 

 orange). 



Crenodonta perplicata (Conrad). 

 One male, and two females, from Bayou Pierre, De Soto Parish, 

 Louisiana, collected Aug. 6, 1910, have been received from L. S. Frier- 

 son. One of the females proved to be gravid, and in the act of dis- 

 charging glochidia. Three males, three females, and two young ones 

 from Ouachita River, Arkadelphia, Arkansas, have been sent by H. E. 

 Wheeler. 



