276 AXEL A. OLSSON 



cream-white, uniform, or in concentric bands due to small difference in 

 shade and intensity. Cavity of the shell white, the adductor scars subequal 

 and distinct, the pallial sinus small, extending not quite to the middle. 



Length 32 mm., height 26.4 mm., diameter 19.6 mm. Guanico, Panama. 



Length 32.6 mm., height 26.4 mm., diameter 18.6 mm. Santa Elena, 

 Ecuador. 



There is some uncertainty as to the identification of this species. The 

 specimen described and figured by Sowerby in the Thesaurus represents 

 a small shell marked with arrow-shaped lines on the umbones and its outline 

 is also more rounded. Hertlein and Strong's figure also shows a small shell 

 with stronger markings. 



Our specimens resemble P. consanguineus (C. B. Adams) but they 

 differ by their larger, fuller umbones, and the anterior end appears more 

 inflated and rounder. All our shells are white or plain, without zigzag 

 markings. 



Range — Panama to Ecuador. Panama: San Carlos, Guanico. Ecuador: 

 Charapota; Manta; Santa Elena, 



Pltar (Pitar) helenae, new species Plate 45, figures 2, 2a 



Shell small or medium in size, ovate, cordate, with full, convex umbones 

 placed near the anterior one-third, the small beaks adjacent, the two ends 

 similar, the anterior one being more narrowly rounded. Lunule large, cor- 

 date, impressed, defined by a weak line. Surface plain, smooth or irregularly 

 wrinkled by concentric lines. Base color of the shell is a light cream, heavily 

 rayed with brown rays and angular markings, the beaks stained with 

 purple and a median lighter ray. Valve margins smooth. Interior white, or 

 faintly blotched with purple in the umbonal cavity. Pallial sinus rather 

 large but not long, broadly rounded at the end. 



Length 23.8 mm., height 19.3 mm., diameter 14.2 mm. Vicinity of Pearl 

 Islands, Panama. Holotype, ANSP 218899. 



Named as a tribute to Mrs. Helen Lee Beil, an enthusiastic collector 

 of Panamic shells. 



Range — Panama. Panama: probably in the vicinity of Pedro Gonzalez 

 Island, Pearl Islands, Panama. 



Subgenus HTPHAJfTOSOMA Dall, 1903 

 Type species by original designation, Cytherea carbasea Guppy. Mio- 

 cene of Jamaica. 



Shell like Pitar, s.s. in shape and color but with a series of small arrow- 

 shaped or zigzag punctations, irregularly distributed over the whole surface. 



Pilar (Hyphantttsoma) hertlelni, new species Plate 45, figures 6, 6a 



Shell ovate, quite convex, relatively thin, umbones prominent, full, 

 with the small beaks placed at the anterior one-third. The shell is broadly 

 ovate in shape, the anterior-dorsal margin straight, descending, and when 

 viewed from within, its end appears rounded, its posterior side longer, 

 higher and expanded, its margin rounded. Lunule large, elliptical in shape, 

 defined by a weak line. Surface smoothish, except for fine lines of growth 



