10 PROCEEDINGS OF THE ACADEMY OF [Jan., 



single cardinal of the right valve high and oblique. The lateral 

 teeth are smooth and not very long. 



Length 28.3, alt. 15, diara. 10 mm. 

 " 30.7, " 16.3, " 9 " 



This species stands near iV. macneilii (Lea) , but differs as follows : 

 it is not biangular behind, is relatively longer, the striation less 

 crowded. N. dysoni (Lea) is also broader with the cardinal teeth 

 less compressed. 



^ y 



Fig. 6. — Nephronaias tempisquensis . 



No species of the family has hitherto been reported from the Rio 

 Tempisque, or from any Costa Rican stream draining into the 

 Pacific. 



MUTELID^. 

 Anodontites luteolus (Lea). 



Rio Tempisque, Filadelfia, Jan. 18, 1910, 50 ft. Lea's type of 

 this species was said to be from the Isthmus of Darien, but his 

 figures were drawn from a larger specimen from Lake Nicaragua 

 (Gabb), No. 41833, A. N. S. P. In the single specimen from the 

 Rio Tempisque the hinge line is straight instead of somewhat curved 

 as in the type and that from Lake Nicaragua. 



