446 UNIONIDiE, THEIR SOFT PARTS 



Genus MARGARITANA. 



Margaritana rugosa = Alasinodonta rugosa, Bar. Amer. Jouvn. Sci., vol. vi. p. 278. 



Branchial uterus occupies the whole length of the outer branchiae, brownish, form- 

 ing a large massive lobe which extends below the margin. Branchial very large, 

 rounded below, the inner ones much the larger, free nearly the whole length of the 

 abdominal sack. Palpi rather small, subtriangular, united nearly one-half way 

 down the posterior edges. Mantle rather thin, much thickened at the margin, 

 blackish on posterior basal edge. Branchial opening rather large, with small, brown 

 papilla?. Anal opening rather large, without papillae,* brown on the inner edges. 

 Super-anal opening very large, with a dark-brown line within, united below. Color 

 of the mass salmon. 



Embryonic shell triangular, brown, has hooks. See Journ. Acad. Nat. Sci., vol. 

 iv. pi. 5. fig. 26. Obs. vol. vi. p. 48. 



Mohawk, N. York, J. Lewis, M. D. 



BemarJcs. — Prof. Agassiz says, that A. rugosa, Bar. = Complanaria, Swain., has 

 " both syphonal openings fringed," and the Professor makes it the type of the genus 

 Complanaria ; but none of the specimens which I have examined have the anal 

 syphonal opening fringed ! 



Margaritana marginata = Alasmodonta marginata, Say. Journ. Acad. Nat. Sci., vol. i. p. 459. 



Branchial uterus occupies the whole length of the outer branchiae. Branchiae large, 

 curved below, nearly semicircular, inner ones much the larger, some more or less 

 free near the posterior end of the abdominal sack, others entirely closed. Palpi 

 rather small, suboval, rather transverse, not united at the posterior edges. Mantle 

 very thin, thickened at the posterior and basal margins, beautifully maculate with 

 very dark-brown, subquadrate spots along the outer margin of the palleal border. 

 These spots are more distinct along the anal and super-anal openings, but, on the 

 basal margin, they are closer, and sometimes join so as to form a continuous line. 

 Branchial opening very small, with delicate, brownish, small papillae. Anal opening 

 rather large, without papillae. Super-anal opening large, united below. Color of 

 the mass greenish, inclining to salmon. 



Embryonic shell triangular, white, with hooks. See Journ. Acad. Nat. Sci., vol. iv. 

 pi. 5, fig. 27, and Obs. vol. vi. p. 49. 



Mohawk, N. York, J. Lewis, M. D. 



* Some specimens are crenulate. 



