PANAMIC-PACIFIC PELECYPODA 237 



One well-preserved specimen from the Gulf of California, exact locality 

 unknown, is contained in the Stearns collection. (Dall, 1899.) 



The type at the U. S. National Museum is a white, solid, somewhat 

 worn shell; its surface is more or less chalky, marked with coarse, irregular 

 concentrics with the sagrination showing but faintly. 



Range — Lower California to Nicaragua and the Galapagos Islands, 

 Mexico: Gulf of California (Dall); Santa Inez Bay (Hertlein and Strong). 

 Nicaragua: Corinto (Hertlein and Strong). Galapagos Islands: Galapagos 

 (Hertlein and Strong). 



Orobitella peruylana, new species Plate 35, figure 7 



Shell of moderate size (length between 13 and 14 mm.), slightly con- 

 vex to depressed, subsolid, inequilateral, the anterior side the longer, its 

 dorsal margin descending towards the end which is rounded with a half 

 circular curve, the posterior side short, also rounded. Surface marked with 

 concentric lines, sometimes irregular and banded, overrun with indistinct, 

 microscopic sagrination. Hinge typical of genus. 



Length 13.6 mm., height 10.8 mm., diameter 2.5 mm. (left valve). 

 Holotype, ANSP 218882. 



Resembles 0. steartisi (Dall) but differs by its shape, the anterior- 

 dorsal margin sloping downward and not parallel to the ventral margin as 

 described and figured for that species. 



Range — Peru and probably Ecuador. Peru: Boca Pan. Ecuador: fossil 

 in Pliocene of Punta Blanca. 



Orebitella margarita, new species Plate 35, figure 2 



Shell moderate in size for the genus (our largest about 11.4 mm.), ob- 

 long, boat-shaped, inequilateral, the posterior side a third shorter than the 

 anterior, rather strongly convex the fullest inflation lying along the posterior 

 umbonal slope, the midzone of the valve in front of it lower, impressed, 

 or flattened. Anterior dorsal and ventral margins are usually parallel or 

 nearly so. Surface marked with irregular concentric growth lines. Interior 

 smooth or sometimes with fine, indistinct radial lines. The ventral margin 

 may be straight or deeply indented. No microscopic sagrination. 



Length 8 mm., height 5.7 mm., diameter 2.2 mm. 



Length 11.5 mm., height 7.1 mm., diameter 2.2 mm. Holotype, ANSP 

 218884. 



Easily recognized by its peculiar shape, the mid-zone usually indented. 

 Range — Panama: Beach at San Miguel, Rey Island, Pearl Islands. 



Orobitella seclinra, new species Plate 35, figures 1-lb 



Shell of medium size (length 9 to 10 mm.), broadly, obliquely subovate, 

 depressed to weakly convex, the posterior side short, flatly rounded to sub- 

 truncate. The beaks are small, facing forward over the long, descending 

 dorsal margin, the end rounded. Surface smooth with fine concentric lines 

 but generally assuming an earthy or chalky texture through weathering. In 

 some shells, the surface is covered by a thin, somewhat chalky textured, 



