ortmann: south American naiades. 627 



the latter collected in January. Von IluM'inf-; found j>;ravid females with lasidia on 

 May 28. 



Anal opening entirely open, its inner edge smooth, separated from the branchial 

 opening l)y a mantle-connection. Branchial opening with fine papillae on inner 

 edge. Palpi very large, nearly semicircular, lower margins rounded, posteriorly 

 truncated, without a posterior point. Posterior margins widely separated at 

 base (this is a peculiar feature, not observed in any of the foregoing species). 



Gills long and wide, the inner the wider anteriorly, its anterior end inserted 

 between the posterior ends of the palpi (this is also a peculiar feature). Outer 

 gill with the anterior end at the highest point of the mantle-attachment-line. Inner 

 lamina of inner gill entirely connected with abdominal sac. Gills with well de- 

 veloped septa running in the direction of the gill-filaments, alternately (but ir- 

 regularly so) stronger and weaker in the non-marsupial gills. The inner gill of 

 the female is marsupial, with stronger, more uniform sejjta, which, however, are 

 not more closely set, and have the usual vertical ridges near the outer lamina, 

 projecting into the hmien of the water-tubes. When charged, only the inner com- 

 partment is filled with ova, thus becoming an ovisac, while the outer compartment 

 remains a (secondary) water-tube. Egg-masses only loosely hanging together. 

 Eggs veiy small, according to Von Ihering 0.071 to 0.090 mm. in diameter, while 

 I have found them to be about 0.08 mm. In this species also I have not been able 

 to find mature larvae, but this is one of the species, in which Von Ihering has ob- 

 served the lasidium, which he describes as being 0.1 mm. long. 



63. Anodontites forbesiana (Lea) (1860). 

 Shells: Plate XLIII, fig. 4; Plate XLIV, fig. 3. 

 Simp.son, 1914, p. 1438. 



Additional References. — Anodonta furbesianu \'on Ihering, 1890, p. 158. 

 CoRSi, 1901, p. 457. 

 Glabaris forbesianus Pilsbry & Rush,- 1896, p. 81. 



Type-locality. — Uruguay River. 



Other Localities. ^Rio de la Plata, Colonia, Uruguay (Pilsbr^y & Rush). 



New Localities. — Rio Uruguay (in mud), Uruguayana, Rio Grande do Sul, 

 Brazil (J. D. Haseman coll., February 5, 1909). Fourteen specimens, males and 

 females, all with soft parts. In pond along banks of Rio Negro, Santa Isabel, 

 Uruguay (J. D. Haseman coll., February 11, 1909). Two odd right valves. 



Distribution. — Known only from the Rio de la Plata below the mouth of the 

 Uruguaj', Rio Uruguay up to Rio Grande do Sul, and its tributaiy the Rio Negro. 



