PANAMIC-PACIFIC PELECYPODA 279 



A good hinge of A. gatunensis, the type species of Pitarella, has not 

 been available during this study, but the same features are shown equally 

 as well by its Recent analogue, A. catharia (see PI. 40, fig. 2). In the right 

 valve, the upper rim of the anterior lateral socket forms a transverse 

 lamina which connects directly with the base of the adjacent cardinal tooth, 

 thus dividing the socket space into two sections, the upper one empty. 

 Pitarenns Rehder and Abbott, 1951 is similar to Pitarella, but it lacks 

 the transverse lamina between the lateral socket and the cardinal tooth. 

 The ventral margins of valves of Pitarenus are obscurely crenulated. 



Agrlopoma (Pitarella) catharia (Dall) Plate 40, figure 2; 



Plate 49, figures 5, 5a 



Callocardia {Agtiopoma) catharia Dall, 1902, Proc. U.S. Nat. Museum, vol. 26, No. 



1312, p. 402, pi. 14, fig. 3 "Bay of Panama, 30 fthms." — Hertlein and Strong, 



1948, Zoologica, vol. 33, pt. 4, p. 177, pi. 2, figs. 14, 15. 

 Pitar {Pitarella) catharius (Dall), Hertlein and Strong, 1955, Bull. Amer. Mus. Nat. 



Hist, vol. 107, art. 2, pp. 190, 191, pi. 1, figs. 5, 6, 7, 8, 9, 10; pi. 2, fig. 24. 



Shell large (length SO to 60 mm.), white, strongly convex with large, 

 full umbones and the beaks slightly coiled and directed anteriorly over a 

 large, cordate lunule outlined faintly by a line. In shape, the shell is some- 

 what variable from nearly rounded forms to others with the posterior side 

 somewhat produced and its margin weakly sinuated. The surface is colored 

 white, often somewhat earthy or chalky, more or less shiny in the middle 

 and marked with fine, close, concentric threads between narrowly grooved 

 interspaces, these concentrics usually coarser on the two ends, often sub- 

 obsolete in the middle so that the surface of the beaks and midzone of 

 the shell appears smooth and polished. Interior mostly white but in some 

 cases with a faint salmon flush in the cavity of the beaks. Adductor scars 

 are fairly small, subequal, the posterior one a little more rounded and with 

 the pallial line running near the margin, its sinus exceptionally wide and 

 shallow, bluntly rounded at the end. 



A typical specimen measures, length 53.8 mm., height 44 mm., diameter 

 33.3 mm. Bay of Panama. 



This species is related to A. gatunensis (Dall) from the Gatun Miocene 

 of Panama and the Canal Zone but the fossil shell is usually smaller, longer, 

 and more inflated. A. {Pitarella) tumbezana Olsson from the Miocene of 

 northern Peru, is another closely related species. 



Pitar tomeanus Dall, 1902, a Chilean species, has been recorded by 

 Dall and others from the Panama region, but the occurrence seems doubt- 

 ful; the small shells figured as such by Hertlein and Strong, 1955 {op cit., 

 p. 190, pi. 2, figs. 1, 2, 5, 6) seem to be young specimens of A. catharia; 

 similar shells are in my collection from several places along the coast of 

 Ecuador. 



Range — Lower California south to Ecuador. Panama: Bay of Panama, 

 (shrimpers); as fossil at Charco Azul. Colombia: Octavia Bay (Hertlein 

 and Strong). Ecuador: Esmeraldas. 



