? 



PANAMIC-PACIFIC PELECYPODA 417 



which cover most of the disk in front of a smooth band along the posterior- 

 umbonal slope. 



The generic relations of Tellina cognata, the type species, has long 

 been controversial; it was referred to Psammobia by Reeve; to Quadrans 

 by Dall; and to Scissula by Hertlein and Strong. The squat rhombic shape 

 of its valves and oblique surface sculpture is strongly suggestive of the 

 Psammobiidae but the nymph is tellinoid, small, and narrow. The cardinal 

 teeth are all bifid and there are no laterals. 



Psammothalia cognata (C. B. Adams) Plate 67. figures l-lb; 



Plate 68, figure 16 p^ 

 > 



Tellina cognata C. B. Adams, 1852, Ann. Lyceum Nat. Hist. New Yorlc, vol. 5, pp. f"" 



503, 545, No. 459.— Turner, 1956, Occas. Papers on Mollusics, Mas. Corap. Zoo!., 



vol. 2, No. 20, p. 38, pi. 18, figs. 9, 10. 



Tellina concinna C. B. Adams, 1852, op. cit., pp. 504, 546, No. 461. — Turner, 1956, op. f" 



cit., p: 41, pi. 18, figs. 16, 17. ~ 



Psammobia casta Reeve, 1857, Conch. Icon., vol. 10, Psammobia. pi. 8, fig. 55. Not Tellina CO 



casta Hanley, 1844. (Guatemala). ^PQ 



Macoma {Psammacoma) cognata (C. B. Adams), Maxwell Smith, 1944, Panamic Marine *ch,^ 



Shells, p. 65, fig. 849. >> 



Tellina {Scissula) cognata C. B. Adams, Hertlein and Strong, 1949, Zoologica, vol. 34, ^-j 



pt. 2, No. 9, p. 85. ^ 



■^ 



Shell with oblong, rectangular valves, slightly convex to depressed, 



the anterior end obliquely rounded, the posterior side shorter, depressed, ' 



its margin straight as if crudely truncated. Surface color is principally ^ 



white except for the umbones which may be shaded lightly with salmon- ^> 



pink or brown; the interior often pink. The surface is generally smooth ^T 



and polished, the growth lines showing indistinctly and sometimes under a y^ 



lens, fine radial striations may often be seen, but the principal sculpture is f^ 



formed by a series of evenly spaced, diagonal, incised lines which begin ^J 



in front of a smooth ray bounding the posterior-umbonal angle. The perio- ^] 



stracum is straw-gray in color, thin and preserved only on live shells. 1^/°\ 



Length 53.7 mm., height 35.8 mm., diameter 15.1 mm. Tumbez, Peru. 



Length 65.5 mm., height 41 mm., semidiameter 9 mm., a right valve, -^ 

 Zorritos, Peru. 



O 



This species, long misunderstood and poorly represented in most 

 museum collections, is now known to be common and widely distributed. P_,^ 



A smooth form or one without the obliquely incised lines was named * 



concinna by C. B. Adams. It is a common fossil in the Pliocene of Ecuador. ,,^^^ 



The same species or a similar one has recently been discovered in the Gulf ^I 



of Mexico and seen by the author (Steger collection, Tampa, Florida). 7^ 



Range — Mexico to northern Peru. For northern records, see Hertlein lys 



and Strong. Panama: Bucaro; San Carlos. Panama Canal Zone: Venado 

 Beach. Ecuador: Sua, Charapota, Playas. Peru: Tumbez; Zorritos; Boca 

 Pan. 



Genus ARDEA3IYA, new genus 



Type species, Tellina columbiensis Hanley. Panama-Pacific. 



Shell elongate-elliptical, subequivalve, inequilateral, compressed or 

 slightly convex, thin, smooth, white. Posterior side somewhat shorter, 

 pointed or wedge-shaped at the end, straight or with the right valve weakly 

 flexed. Hinge plate small forming a narrow roof or shelf above the umbonal 



i^ 



