22 



TRIGONIAN A 



918 Trigoxia pectmata. Lam., New Holland. Asiroi. pi. 78, f. 1-4. 



N A I A D A 



919 Unio* 



MARGARITA, 

 acutissimus, Lea, Alabama. 



Trans. Am. P. S. pi. -x. f. 18, v. 4. 



* In the arrangement of the Naiades I have adopted the classification of Isaac Lea, Esq. of Philadelphia. His 

 " Synopsis of the family Naiades of Lamarck," and also descriptions of several new species, illustrated by beauti- 

 fully colored plates, have lately appeared in the Transactions of the American Philosophical Society, Philadelphia, 

 Vol. VI. Part I. New Series. 1^38. 



