THE NAIADES OF MISSOURI 1 77 



sculptured by fine concentric ridges disposed somewhat like that of 

 with those from the Mississippi to find them precisely identical in 

 every respect. 



Eurynia (Eurynia) recta (Lamarck).' 



("Spectacle-Case," "Black Sand Shell.") 



PI. XXVII; Figs.joo A—D. 



1 819 — Unio recta Lamarck, An. Sans. Vert., VI, p. 74. 



1823 — Unio praelongus Barnes, Am. Jl. Sci., istser., VII, p. 261, fig. 11. 



1900b — Lampsilis rectus Simpson, Pr. U. S. Nat. Mus., XXII, pp. 



544-545. 

 1912b — Eurynia {Eurynia) recta (Lam.) Ortmann, An. Car. Mus., 



VIII, p. 344. 



ANIMAL CHARACTERS. 



Nutritive Structures: — Branchial opening with numerous 

 papillae; anal finely crenulate; supra-anal separated from anal 

 by moderate mantle connection; inner laminae of inner gills con- 

 nected to visceral mass; palpi small, almost entirely free along 

 their antero-posterior edges; color of soft parts grayish with its 

 posterior mantle border blackish or reddish brown. 



Reproductive Structures : — Marsupium rather kidney- 

 shaped consisting of fifty large ovisacs extending below the original 

 ventral line into thickened, cream-colored, cone-shaped beads 

 when gravid ; ova lying in irregular masses within the sacs ; mantle 

 edge antero-ventrad to branchial opening specialized with very 

 great number of large, densely crowded papillae extending entirely 

 to the center of the ventral edge; conglutinates white, glochidia 

 rather medium in size, semi-elliptical, spineless, rounded ventral 

 edge, hinge line undulated, measure 0.220 x 0.280 mm. 



SHELL CHARACTERS. 



External Structures: — Elongate-elliptic, heavy, rather 

 thick, large ; female shell broader and more blunt posteriorly than 

 male; no post-umbonal ridge; disk smooth; beaks large, low 

 sculptured by fine concentric ridges disposed somewhat like that of 



' This Species is the most generally distributed of the Lampsilinae. 

 (See accompanying Map (Plate XXIX) for three other generally distributed 

 Species; viz., Cumberlandia monodonta {Say) as representative of Margari- 

 tanidae, Quadrula verrucosa {Raf.) of Unioninae and Strophitus edentulus 

 {Say) of Anodontinae. 



