ortmann: south American naiades. 



557 



elongated) shape, which makes the beaks appear to be rather far back (in comparison 

 with baro). However, this may be only a more aged form of acuticosta. 



34. C'astalia baro (Von Ihering) (1910) 

 Castalia ambigua Sowerby (not Lamarck), XVII, 1869, PI. 1, fig. 1. 

 Tetraplodon baro Von Ihering, 1910, p. 127; Simpson, 1914, p. 1198. 



Type-locality. — -Amazon River. 



New Locality: Sand bar of Rio Tapajos, Santarem, Para, Brazil (J. D. Hase- 



man coll., December 6-12, 1909). One complete shell, two odd valves, right and 



left. 



In addition the Carnegie Museum has two other fine specimens, one from the 



Holland collection, labeled "River Amazon," the other from the Juny collection, 



without locality. 



Distribution: Amazon and Tapajos Rivers. 



This species stands very close to C. hanleyana, and differs only in its more 

 elongated shape, and, consequently, more anterior beaks. Von Ihering says that 

 the lower margin is straight (while it is convex in hanleyana). But this feature is 

 somewhat variable, for it may be gently curved. However it is correct that in 

 baro the lower margin is more nearly straight than in hanleyana. 



I should not be astonished if hanleyana and baro should finally prove to be 

 only the adult stages of acuticosta. The fact that all three have been found by 

 Haseman associated at Santarem is in favor of this view. 



About the dimensions of baro we only know that the beaks are at 16 pr. ct. of 

 the length. My specimens show a somewhat higher percentage, but not as high 

 as in hanleyana (where it is from 28 to 33 pr. ct.). 



Measurements. 



35. Castalia pectinata (Spix) (1827). 

 Tetraplodon pectinatum Spix, 1827, PI. 25, fig. 3; Von Ihering, 1910, p. 125. 

 Unio pectinatus Wagner, 1827, p. 32. 



Castalia ambigua Von Ihering (not Lamarck), 1890, p. 162. 

 Type-locality. — Rio Sao Francisco, Minas Geraes, Brazil. 



