ortmann: south American naiades. fill 



eggs in their inner compartments, except at the anterior and posterior ends of 

 the gill; the other compartments forming secondary water-tubes. The septa 

 of the ovisacs are somewhat stretched out, and the gill is slightly distended. I 

 was unable to find fully developed larvic (lasidia?). All eggs are small, round, 

 globular masses of cells (morula-stage), enclosed in a rather tough membrane. 

 In the males no regular alternation of stronger and thinner septa could be noticed, 

 but all septa are rather imiform. The male character, however, has been positively 

 established by microscojiic examination (absence of swellings of the septa). 



5. Group of Anodontites patagonica. 

 Simpson, 1914, p. 1403. 



Shell stronglj' oblique, subovate or subrotund, not pointed behind. Epidermis 

 more or less shining, but here and there with wrinkles, or covered all over with 

 concentric striae. Prismatic border rather wide and unequal, being much wider 

 along the anterior lower margin than at the anterior and posterior ends. 



The prismatic border forms the most prominent feature of this grouj). I 

 possess a good number of specimens belonging to the group, and this character is 

 alwaj's present, so that we must regard it as of taxonomic value. In addition 

 the shell is here distinctly oblique with a rounded end. 



Key to the Forms at Hand. 

 Oi. Shell moderately inflated, diameter generally between 40 and 50 pr. ct. of the length, rarely less. 

 Outline strongly oblique, moderately elongate, sometimes sul)r(itund, height from about 0.5 to 

 over SO pr. ct. of length. 



foi. Shell thick, rather more elongated. Nacre whitish .4. palngonicn. 



bo. Shell thinner, subrotund or elongated. Nacre often red.. .4. patagonica riibiriinda. 



0;. Shell compres.sed, diameter 36 pr. ct. or less. Outline obliquely ovate, rather elongated, height not 

 over 66 pr. ct. 



bi. Prismatic border wide and unequal. Epidermis shining, stria? not sublamellar 4. puclchana. 



bn. Prismatic border narrower, but unequal. Epidermis not very shining, with the stri:p often 

 sublamellar 4. iheringi. 



bl . Anodontites patagonica (Lamarck) (1819). 

 Anodonta patagonica Lamarck, 1819, p. 88; Encyclop. Method., 11, 1827, p. 147, 



PI. 203, fig. 1. • 



Anodontites patagonicus Simpson, 1914, p. 1403. 



Remarks as to Synonymy. — The synonymy of this species has been given by 

 Simpson, but it needs certain additions and corrections. The following references 

 should be added first of all : 

 Anodonta latemarginala and urtigiKiycnsis ( "ursi, 1901, p. 454, 458. 



