ORTMANN: FAMILIES AND GENERA OF NAJADES. 307 
Septa of the non-marsupial gills as usual. Marsupium formed by 
the outer gills in almost their whole length; only small sections are left 
free anteriorly and posteriorly; but in young individuals larger sections 
are non-marsupial. In the basal half the whole outer gill is non- 
marsupial, and has rather wide water-tubes, but the marginal half 
becomes marsupial, with much narrower water-tubes (ovisacs), and 
along the edge of the gill the ovisacs bulge out beyond it. This 
bulging out is only moderate. The placente are in the distal half of 
the gill; they are subcylindrical and club-shaped, being thicker toward 
the edge. The whole marsupium is thrown into a number of folds, 
increasing its surface, and further, in the distal part of the gill, the 
filaments are stretched or flattened out, so that the membranes en- 
closing the placenta become much thinner in this region than usual. 
Along the edge of the marsupium, the protruding ovisacs appear as a 
folded series of beads. The number of the ovisacs and of the folds is 
variable, and increases with age. Also in the sterile female the 
beads and folds are indicated on the edge of the marsupium. 
Placentz quite solid and permanent. They are discharged whole 
through holes formed at the end of the ovisacs (repeatedly observed). 
A brown stain is developed in the placentz, chiefly on their surface, 
which possibly indicates a hardening of the gelatinous matter. The 
eggs and glochidia are imbedded uniformly through the placental 
mass, but they are most crowded at the swollen ends. 
Glochidia (see Lea, Obs., VI, 1858, pl. 5, fig. 12;34 and Ortmann, 
1911), pl. 89, fig. 14) rather small, subovate, without hooks, higher 
than long. Length 0.17; height 0.19 mm. 
Color of soft parts whitish, foot grayish, gills whitish, or grayish 
brown. Edge of mantle brown, broadly black posteriorly. Marsu- 
pium, when charged, blackish or purplish brown, inclining sometimes 
more to blackish, sometimes more to purple. Beads at edge more 
vividly colored, red or purple. A line of black markings near the 
edge, immediately below the protruding beads, on each side. 
34 The poor quality of Lea’s figures of the glochidia is clearly shown in this in- 
stance. The figure of the glochidium of phaseolus (fig. 12) stands next to that of 
Eurynia recta (fig. 11), and is distinctly larger than the latter, while actually the 
glochidium of E. recta is by far the larger of the two. Also the outlines of these two 
glochidia are not quite correctly rendered. 
