Freshwater Species 



33 



Psoronaias quadratus (Simpson) 



Illustration: Coe, 1959, fig. 52,^. 



Archaeological occurrence: 



PIEDRAS NEGRAS: i unworked in Late Clas- 

 sic burial (C, p. 55, fig. 52,^), as "Ouadrula 

 quadrata," which is this species). 



Psoronaias semigranosus (v. d. Bush) 

 Illustration: Plate 21,^. 

 Archaeological occurrence: 



DZIBILCHALTUN: 4, pierced for suspension, 



in Late Formative tomb; 3 unworked, Late Early 

 period. 



MAYAPAN: i, pierced, probably Decadent pe- 

 riod (P, p. 387, fig. 44,^). 



Comment: Unclassified freshwater clams have been 

 listed from Uaxactun by the Ricketsons (RR, p. 

 199) and by Kidder (p. 61). Moholy-Nagy lists 61 

 slightly altered (usually pierced) Unionidae clams, 

 including five paired valves, and a smaller number 

 of unworked valves (M— MS). 



