PANAMIC-PACIFIC PELECYPODA 42S 



SO as to resemble a small Hiatella arctica, its end in consequence more 

 broadly truncate. The posterior-dorsal slope is set apart by a small umbonal 

 angle. Surface marked with coarse, often wrinkled growth lines, heaviest 

 on the posterior slope, and covered by a thin, skinlike, light-colored epider- 

 mis. Interior with the adductor scars quite large, subequal, and showing 

 prominently. Pallial sinus large, rounded but relatively shallow. 



This is a small nestler inhabiting abandoned worm burrows, hence 

 extremely variable in shape. Specimens in the U. S. National Museum 

 labeled S. fragilis from California and Oregon are much larger than any seen 

 from the Panamic province and should probably be referred to another 

 species. S. trunculus Dall, described originally from San Diego, California, 

 has been recorded from Panama (specimens, USNM), but they are 

 probably only a form of S. fragilis. 



Range — Oregon? to northern Peru. Mexico: Mazatlan (Carpenter). 

 Panama: Panama City and numerous other localities. Panama Canal Zone: 

 Venado Beach. Ecuador: Esmeraldas. Peru: Zorritos. 



Family HIATELLIDAE 



Shell usually ovate or oblong, generally irregular due to distortion, 

 widely gaping behind, byssiferous. Surface smooth but more often with 

 irregular concentric riblets or undulations. Hinge weak, the teeth often 

 obsolete, no laterals, the ligament external, attached to a strong nymphal 

 ridge. Pallial sinus of irregular size, the animal provided with large siphons. 

 Burrowing in deep sand, gravel, or as nestlers or borers in rock. 



Genus HIATELLA Daudn, 1801 

 (Saxicava Bellevue, 1802 is a synonym.) 

 Type species by subsequent designation, Hertlein and Strong, 1850, 

 Hiatella biaperta Bosc {=Mya artica Linne). North Atlantic. 



With the characters of the family. 

 Hiatella sollda (Sowerby) Plate 77, figures 6, 6a 



Saxicava solida Sowerby, 1834, Proc. Zool. Soc. London, pp. 88, 89 (ad Sanctain 



Elenam). — Reeve, 1875, Conch. Icon., vol. 20, Saxicava, pi. 1, fig. 6. — Sowerby, 



188+, Thes. Conch., vol. S, p. 133, No. 7, pi. 471, fig. 12. 

 Saxicava tenuis Sowerby, 1834 op. cit., p. 88 Pacosmayo et ad Lambeyeque. — Reeve, 



1875, op. cit., pi. 2, fig. 9.— Sowerby, 1885, op. cit., pi. 471, fig. 11. 

 Saxicava purpurascens Sowerby, 1834, op. cit., p. 88 ad Insulam Muerte. — Reeve, 1875, 



op. cit., pi. 2, fig. 14.— Sowerby, 1884, op. cit., pi. 471, fig. 7. 

 Hiatela arctica (Linne), Hertlein and Strong, 1950, Zoologica, vol. 35, pt. 4, pp. 244, 



245. 



Generally subrectangular, longer than high, inequivalve, the right 

 valve deep and higher than the left at the umbones, the anterior side short 

 and sloping, but the shell variable in shape and thickness. The posterior 

 side is generally drawnout, often with a strong, umbonal ridge running to 

 the posterior-ventral margin and another smaller one along the dorsal mar- 

 gin. Color yellow, brown, or more or less purplish. 



Because of wide differences in size and shape, due mostly to distortion 

 or other accidents of growth, several names have been given to this shell. 

 Some authors consider this species the same as the widespread, boreal H. 

 arctica (Linne) but for the present, it seems best to regard the South 

 American form as distinct. 



