ortmann: south American naiades. 639 



ticular advantage in this. Yet the length of the hinge-line from its anterior end 

 to the anterior end of the ligamental sinus, and its proportion to the length of the 

 shell, should be noted, because there are slight differences in our specimens in this 

 respect. 



According to Hupe's figure, the beaks are located at 44 mm. = 32 pr. ct. of 

 length. This and the height given by Von Ihering agree very well with my speci- 

 mens, but the proi)ortion of the hinge-line to the total length is less in the latter. 

 But the figures for my specimens show that that there is variation in this respect. 



BIBLIOGRAPHY. 



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1906 Bartsch, p. Descriptions of Two New Naiades (Proc. U. S. Nat. Mus., XXX, 

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1900-1901 CoRsi, A. F. Moluscos de la Republica Oriental del Uruguay (Anal. Mus. 

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1915 Frierson, L. S. A New Pearly Freshwater Mussel of the Genus Hyria from 



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Zool., No. 25, 1916, pp. 1-63). 



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 1857 Hupe, H. Mollusques, in Castelnau, F. De, Animaux nouveaux ou rares 



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