260 AXEL A. OLSSON 



Key to the species of Dosinidia in the Panamic-Pacific region 



I. Shell of medium or large size (length 75 mm. or more), suborbicular, 

 subsolid, the sculpture formed by rather large, wide, concentric rib- 

 bons, usually weaker or subobsolete across the middle of the disk. 



D. fonder OS a 



II. Shell smaller (generally less than 50 mm. in length). 



1. Pallial sinus relatively short, hardly extending to the middle of the 

 shell cavity. Sculpture usually smooth across the middle of the disk. 

 Uncommon, 



D. annae 



2. Pallial sinus longer, extending past the middle of the shell cavity. 

 Concentric sculpture fairly strong and uniform over the whole disk. 



D. dunkeri 



Dosinia (Dosinidia) ponderosa (Gray) Plate 40, figure 5; 



Plate 42, figures 1-lc; Plate 43, figure 1 



Arthemis ponderosa Gray, 1838, Analyst, vol. 1, p. 309. 



Cytherea {.Artemis) gigantaea Sowerby, Philippi, 1847, Abbild. und Beschreib. Conchylien, 



bd. 2, Cytherea, p. 231, Cytherea taf. 7, figs, la, b, c. 

 Artemis ponderosa Gray, Reeve, 1850, Conch. Icon., vol. 6, Artemis, pi. 1, fig. 4 "Gulf 



of California".— Sowerby, 1852, Thes. Conch., vol. 2, Artemis, p. 656, No. 3, 



pi. 140, fig. 2. 

 Dosinia ponderosa (Gray), Romer, 1862, Mon. Molluskengattung Dosinia, Scopoli, p. 



12, No. 6.— Dall, 1909, Proc. U.S. Nat. Museum, vol. 37, No. 1704, p. 265. 

 Dosinia {Dosinidia) ponderosa (Gray), Hcrtlein and Strong, 1948, Zoologica, vol. 33, 



pt. 4, p. 165. — Hertlein and Strong, 1955, Bull. Amer. Mus. Nat. Hist., vol. 107, 



art. 2, pp. 188, 189. 



SOME FOSSIL RECORDS 



Artemis ponderosa Gray, Darwin, 1844, Geol. Obser. ed. 1; 1891, same, 3d ed., pp. 403, 

 405 Coquimbo, Chile.— Philippi, 1887, Die Tert. u. Quart. Versteinerungen 

 Chiles, p. 113, pi. 14, fig. 5 (Coquimbo, the figure is taken from a Recent 

 specimen). 



Dosinia grandis Nelson, 1870, Trans. Connecticut Acad. Sciences, vol. 2, p. 201 Peru. 



Dosinia {Dosinidia) grandis Nelson, Spieker, 1922, Johns Hopkins Studies in Geology, 

 No. 3, pp. 138-140, pi. 8, fig. 4 Peru.— Palmer, 1927, Paleont. Amer., vol. 1, 

 p. 275, pi. 17, fig. 12; pi. 19, fig. 8; pi. 20, fig. 14; pi. 45, figs. 1-4.— Olsson, 

 1932, Bull. Amer. Paleont., vol. 19, pp. 105, 106. 



Dosinia {Dosinidia) titan Maury, 1925, Bull. Amer. Paleont, vol. 10, No. 42, pp. 291, 

 292, pi. 24, figs. 1, 2; pi. 25, fig. 3 Miocene, Trinidad. 



Dosinia ponderosa (Gray), Grant and Gale, 1931, Mem. San Diego Soc. Nat. Hist, 

 vol. 1, p. 351, pi. 15, figs, la, lb, Ic; also variations, pi. 15, figs. 2a, 2b, 3 

 {jacaltosana Arnold); pi. 15, fig. 4 {longidens Grant and Gale). — Durham. 

 1950, Geol. Soc. America, Mem. 43, p. 84, pi. 22, figs. 3, 6 (Lower California). 

 — Woodring, 1951, U.S. Geol. Survey, Prof. Paper 222, pp. 64, 89, 104, pi. 

 16, fig. 6; pi. 19, fig. 1; pi. 20, fig. 7 California. 



Adult shell large ( length to about 145 mm.), orbicular, the posterior 

 side wide, convexly vaulted across the middle, solid in texture, white. 

 Sculpture formed by rather wide, concentric ribbons, often divided on the 

 sides, much wider on the middle zone or partly obsolete there. The lunule 

 is small, its surface deeply impressed. Adductor scars are large, smooth, 

 polished, connected by the pallial line with a deep sinus reaching to the 

 middle of shell cavity. 



This is the largest species of Dosinia, also recognized by its orbicular 

 shape, and coarse, wide concentric ribbons which often fade out over the 

 middle zone of the disk. As a late Miocene, Pliocene, and Pleistocene fossil, 



