ART. 12 NEW LAND AND FRESH-WATER MOLLUSKS MARSHALL 7 



The type (Cat. No. 362860, U.S.N.M.) measures : Length, 25.5 mm. ; 

 height, 19 mm.; diameter, 15 mm. It comes from Sinu River at 

 Lorica, Province of Bolivar, United States of Colombia, South 

 America, and was collected and presented by Theodore A. Link of 

 the Tropical Oil Co. Lorica is in the northwestern corner of Co- 

 lombia, near the mouth of the Sinu River, which empties into the 

 Gulf of Morosquillo, an arm of the Gulf of Darien, Caribbean Sea. 



The lot sent by Mr. Link included also fifteen-odd valves (Cat. 

 No. 362861, U.S.N.M.). Some of these are older and larger than 

 the type, the largest measuring : Length, 42 mm. ; height, 28.5 mm. 

 These larger specimens show that the radiating ribs are not devel- 

 oped or have a tendency to become obsolete in the portion of the 

 shell formed after the size of the type has been attained. 



The only species to which this is closely related is Tetraijlodon 

 ecarinafa Mousson, which occurs in the Magdalena River, United 

 States of Colombia. Ecarinata is less elongate, of rounder form, has 

 the ventral margin more arcuate and the radiating ribs rounded 

 instead of flattened. 



HYRIA WHEATLEYI, new species 



Plate 1, figs. 3, 5 ; plate 3, fig. 1 



Shell small, solid, somewhat inflated, subrhomboid, wide and 

 nearly squarely truncate posteriorly, narrow and oblique anteriorly; 

 very slightly alate at both ends. Hinge line slightly arched; pos- 

 terior and anterior margins making distinct (nearly right) angles 

 with the dorsal margin. Ventral margin curved, sloping rather 

 sharply into the anterior margin which is very short. Greatest diam- 

 eter at the center of the shell, anterior ridge lacking, posterior ridge 

 high, rounded, made to appear sharp by one of the radiating ribs 

 of the beak sculpture running along its summit. Concentric sculp- 

 ture of fine striae with two rest periods accentuated by a dark line. 

 Beak sculpture radial, very bold and regular, consisting of 16 con- 

 tinuous principal ribs, one on the posterior ridge and the others 

 anterior to it, and several interrupted minor riblets on the posterior 

 dorsal area. The six middle ribs are arranged into three " nested " 

 pairs, the two ribs in each pair converging and pointing ventrally. 

 If continued other ribs would converge in pairs thus "nested." In- 

 terior iridescent pearly, appearing to be finely, radially striated, 

 the striae more marked along the ventral margin. Pseudocardinal 

 teeth of right valve two, the inner one large and divided into four 

 denticles; the outer one small, low and linear. Pseudocardinal of 

 left valve with a large socket. Lateral tooth of right valve high, 

 slightly curved, obscurely striated, vertically and obliquely. The 

 two lateral teeth of left valve distincty obliquely striated, the inner 

 tooth the higher. Anterior adductor scars deep, especially at the 



