ortmann: south American naiades. 501 



rupted septa are seen anj-where. That these septa are onlj^ a modification of the 

 scattered interhiminar connections is shown by the fact that the latter are found 

 in the non-marsupial gills (See outer gill on PI. XLV, fig. 4h, and gills of male, 

 PI. XLV, fig. 4a). All four of my large females show this arrangement, and in 

 the two young ones traces of the beginning of this structure are seen. The em- 

 bryos fill the water-tubes in loose masses, not forming distinct placentae. 



Glochidium (Text-fig. 4c, p. 469) mucli like that of D. ricariuf;, oblique, L. 

 0.31, D. 24 mm., with hooks, 0.09 to 0.11 mm. long. One specimen has immature 

 glochidia, but rudimentary hooks can be seen. The date of collecting (December 

 23) gives a hint as to the breeding season. 



While this species is very close to the three preceding in the characters of 

 the shell, it has differences in the soft parts, which are very striking. The structure 

 of the marsupium is extremely interesting, and there is no doubt that it must be 

 regarded at least as of specific value, representing a high specialisation of this 

 organ. 



12. DiPLODON PAULisTA (Vou Iheriug) (1893). 



Anatomy of gills: PI. XLM, iig. 1. Section of gilh: PL XLVIII, fig. 1 ; 

 Glochidium: Text-fig. 4 f. p. 4G9. 



Unio paulista Von Ihering, 1893, p. 93, PI. 4, fig. 7. 

 Diplodon paulista Simpson, 1900, p. 873; 1914, p. 1229. 



Type-locality.— ViYSiC\csha., Sao Paulo, Brazil; according to Nehring (1893, p. 

 166) in Rio Piracicaba Mirim. 



New Localities.— nio Tiete, Mogy das Cruzes, Sao Paulo, Brazil (Headwaters 

 of R. Tiete) (J. D. Haseman coll., July 19, 1908) males, barren and gravid females, 

 originally twenty-five in the lot, all with soft parts. Rio Tiete, Sapina, Sao Paulo 

 (Exact location unknowni, but must be near city of Sao Paulo) (J. D. Haseman 

 coll., July 23, 1908) one male with soft i)arts. Creek, tributary to Rio INIogy 

 Guassu, Mogy Mirim, Sao Paulo, Brazil (tributary to Rio Grande and Parana) 

 (J. D. Haseman coll., August 7, 1908) males and gravid females, originally seven- 

 teen specimens in the lot, all with soft parts. 



A detailed description of five specimens has been given by Von Ihering, but 

 the specific characters have remained obscure. The specimens before me agree 

 very well with this description, but it should be noted that the two forms of the 

 shell supposed by Von Ihering to belong to the male and female, do not represent 

 sexual differentiation, but simj^ly individual variations. The more regularly 

 ovate outline, believed to belong to the male, is in fact rather rarely well-developed. 



