AKT. 12 NEW LAND AND FRESH-WATER MOLLUSKS MARSHALL, H 



ventral portions and especially in the adductor scars. General color 

 of interior bluish. Anterior adductor scar moderately deep posterior 

 scar nearly superiScial ; prismatic margin very narrow and of a dark 

 olive color. Pallial line very feebly marked, about 8 mm. from the 

 margin. 



The type, Cat. No. 359920, U.S.N.M., measures : Length, TO mm. ; 

 height, 39 mm. ; diameter, 32 mm. It comes from Venezuela and was 

 received from Mrs. T. S. Oldroyd, of Leland Standford University, 

 to whom a paratype was returned. 



Except for the diflPerences in the character of the hinge this shell 

 in both internal and external features is almost an exact counterpart 

 of specimens of the common Elliptio coiiiplanatus of the United 

 States. Its nearest relative is Anodontites leotaudi Guppy, which 

 comes from the island of Trinidad. 



NOTE ON DIPLODONTITES COOKEI MARSHALL 



A specimen. Cat. No. 3G2862, U.S.N.M., of this species, received 

 from Theodore A. Link, came from the Quebrado Perro, an affluent 

 of the Rio San Jorge, which becomes tributary of the Rio Cauca 

 which later joins the Rio Magdalena, about 200 miles above its mouth. 

 This locality is in the Province of Bolivar, United States of Colom- 

 bia. The locality of the type lot, the only other specimens laiown, is 

 in a tributary of the Rio Colorado, an affluent of the Rio Magdalena 

 tn the Province of Santauder, United States of Colombia. While 

 the known geographic range of the species is extended by the speci- 

 men from Link it remains confined to tributaries of the Rio Mag- 

 dalena. 



This specimen measures: Length, 66 mm.; height, 37 mm.; diam- 

 eter, 29 mm. The largest specimen heretofore known, a paratype, 

 measures: Length, 56 mm.; height, 32 mm.; diameter, 20 mm. The 

 specimen from Link has the appearance of being a very old shell. It 

 has the sculpture and the exact colors of the type, but the ventral 

 edge is somewhat arcuate and the valves widely gape anteriorly. At 

 that point each valve has a shelly growth attached along the inner 

 edge of the prismatic border, forming a little shelf about 17 mm. 

 long and 6 mm. wide, reaching inward as far as the pallial line. Its 

 free edge is dark and resembles a prismatic border and may be one. 

 Its exposed surface has fine striae like those in the periostracum of 

 rhe shell. The indications are that the edges of the mantle were 

 turned back and continued a shell growth directed toward the beaks 

 instead of away from them. 



