6^ American Kast Coast Arcas 63 



from twenty-six in the roundest, A. Holmcsii. to thirty-five in the most elongated, A. 

 atnericana; but the short, round ones often have as many ribs as the elongated speci- 

 mens * * *. The anterior granular series of teeth is much shorter than in A. tolepia, 

 and does not extend much in front of the beaks." — Dall. 



The synonymy is largely taken from Dall. The references to Lister, Schroeter, 

 Gmelin, Bruguiere and Solander are also given by Dillwj^n. Dillwyn's reference to Lis- 

 ter, Enc. Meth., t. 310, f. 1, is incorrect. The A. ovalis included in the synonymy is not 

 Af ovalis Gabb, (Acad. Nat. Sci. Phila., Journ., 2d ser., vol. 8, pp. ^291, 321, pi. 41, figs. 

 10, loa), from the Cretaceous of Peru. European fossils have also been named A. ovalis. 



Dimensions. — Long form. Ion. +21, -45; alt. +7,-50; semidiam. 23 mm. Round 

 fonn. Ion. + 15, -35; alt. +5,-38; diam. 36 mm. 



Occurrence. — "The species does not descend below the uppennost Miocene, if, in- 

 deed, any of the specimens are so old. I have only identified it with certainty from the 

 Pleistocene of Georgia, of Simmons Bluff, South Carolina, of New Jersey, and southern 

 New England." — Dall. Pleistocene of Grand Chenier, Pumping Station no. 7, and New 

 Orleans, Louisiana and Georgetown, South Carolina; recent from Cameron and Point- 

 au-Fer, Louisiana; Galveston, Texas. Mobile, Alabama, Ft. Barrence, Florida, and from 

 South Carolina. — C. U. Mitseian. 



Scapharca (Argitta) tolepia Dall; Plate XV, Figures 14, 15; (Wagner Free Inst. 

 Sci., Trans., vol. 3, p. 649, pi. 33, figs. 7, 8, 1898), from the Oligocene of Rio Amina, St. 

 Domingo; Bowden, Jamaica, and Cumana, ^'enezuela, is smaller (28 mm. long) than A. 

 cavtpec/ietisis, is much more inflated and rotund and has finer and more nodulose sculp- 

 ture. It has about thirty-four ribs. Dall places in synonymy with his species the Area 

 pexata listed by Guppy, (Geol. Mag., Oct. 1874), fossil from Caribbean beds. Guppy 

 also listed .-i . /if.va/iJ Say from St. Domingo and Cumana in Quart. Journ. Geol. Soc. 

 Lond , vol. 22, pp. 575, 576, 1866. Among fossils from. St. Domingo in the C. U. Mu- 

 seum there are specimens belonging to several small, inflated species varying from Argina 

 to section Scapharca. 



Section Bathyarca, Kobelt 

 '"Group of A. peel inicitlijiiics Scacchi (/Jal/iyarca Kobelt, 1891.) 



■'Shell small, usually abyssal, inflated, with prosogyrate beaks and a rather narrow 

 but long furrowed area, the hinge-margin nearly or quite as long as the shell; teeth few, 

 oblique, in two series, often separated by a wide gap in the center: the right valve 

 smaller, the sculpture of the two valves often very discrepant ; epidermis usually imbri- 

 cated. 



"These small deep-water Arks go back to the Eocene in time and fonn a verj- rec- 

 ognizable group, related to Scapharca as Lissarca is to Barbatia." — Dall. 



Scapharca (Balhyarca) Hcndcrso7ii YiaW; Plate XYI, Figure i; (Dall, Wagner Free 

 Inst. Sci., Trans., vol. 3, p. 653, pi. 33, fig. 9, 1898), from the Oligocene of the Bowden 

 beds, Jamaica, is very small (2 mm. long), "much inflated, the hinge-line as long as the 



