1 60 THE NAIADES OF MISSOURI 



tical, inflated; disk smooth; beaks high and full; post dorsal 

 ridge somewhat alated; post umbonal ridge biangulated; epidermis 

 i^lossy black. 



Internal Structures: — Cardinals double in both valve; 

 laterals prominent, blade-like; umbonal and branchial cavities 

 deep and rounded out; nacre rich purple. 



Sex Length Height Diameter Locality 



o^ 120 X 75 X 53mm (White R., Hollister) 



9 125 X 70 X 44mm 



d' 83 X 56 X 40mm 



9 70 X 47 X 34mm 



Miscellaneous Remarks: — The young shells of P. purpurata 

 are thin and fragile but later become thick and solid; resembling 

 alaia in form and nacre but is more so alated not compressed. 

 This shell only appears in the White and Neosho River basins 

 and is one of the few not found in the Mississippi. Its favorite 

 habitat is deep water and mud bottoms. It is hoped its glochidium 

 may be verified and more proportionate measurements given 

 than Lea was able to record. 



Proptera laevissima (Lea). 



("Paper Shell," "Double Wing.") 



PL IX, Figs. 19 and 20; PI. XXVI, Figs. 94 A—D. 



1830 — Symphynota laevissima Lea, Tr. Am Phil See, III, p. 444, 

 pi. XIII, fig. 23. 



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



P- 5 74- 



1912b — Proptera laevissima (Lea) Ortmann, An. Car. Mus., VIII, 



P- 334- 



ANIMAL CHARACTERS 



Nutritive Structures: — ^Branchial and anal openings very 

 tubular, directed away from each other; anal smooth; supra-anal 

 high, well separated from anal by mantle connection; inner 

 laminae of inner gills entirely connected to visceral mass; palpi 

 broader than long, connected about one-half of the length antero- 

 dorsad; color of soft parts a modest tan, except for mantle edges 

 at siphonal openings and the area over nephridium. 



Reproductive Structures: — Marsupium large, kidney- 

 shaped occupying over half of posterior part of outer gills and 

 consisting 50-60 narrow ovisacs somewhat distended transversely 



