Catalogue of Land and Fresh Water Shells. 



99 



13. Unio crassidens, Lam. 



L. 2^ and over, H. 1^ and over. Dark, sometimes black, 

 nacre yellow salmon color. Female abrupt on posterior. 



14. Unio crassa, Say. 



L. 5^ and over, H. 2 and over. Yellow or dark, rayed with 

 green. Female shorter and more abrupt. 



15. Unio cylindrica, Say. 



L. 3 and over, H. 4^ and over. Hinge line straight and 

 and long, under edge of base, concave, noduled and 

 wrinkled on posterior part. 



16. Unio donaciforma, Lea. 



L. \y 2 and over, H. 1 and over. Green covered with zigzag 

 rays. 



17. Unio dorfeuilliana, Lea. 



L. 2^ and over, H. 2]/ 2 and less. Like No. n, but not so 

 ridged, has the dark marks near beaks of No. 48, but is 

 covered with pustules up to the beaks. 



18. Unio ebena, Lea. 



L. 2 and over, H. 2^ and over. Obliquely circular and gen- 

 erally black. 



19. Unio elegans, Lea. 



L. 2, H. 1 5-8. Marked like No. 16, but more triangular and 

 very flat, and abrupt or truncate on posterior part. 



20. Unio ellipsis, Lea. 



L. 2^ and less, H. 2 and less. Elliptical, light yellow with 

 darker rays. 



21. Unio fabalis, Lea. 



L. 1%, H. y±. Dark brown finely rayed with black. 



22. Unio foliata, Hild. 



Female of No. 23 — L. 2^, H. 2. Yellow and finely rayed, 

 A broad sulcus or groove runs from beak to margin near 

 posterior end. 



23. Unio flexuosa, Raf. 



Male — Sulcus broader and deeper than No. 22, making the 

 lower margin of the shell very irregular. 



24. Unio fragosa, Conr. 



L. 3, H. 3 or less. Resembles No. r7, but more pustulate on 

 beaks and a shallow sulcus runs from beaks to margin. 



