122 BULLETIN 90, UNITED STATES NATIONAL MUSEUM. 



The young of Anadara aresta Dall look a good deal like this spe- 

 cies, but have the beaks more central and prominent and not mesially 

 impressed. 



Genus GLYCYMERIS Da Costa. 



Glycymeris Da Costa, Brit. Conch., p. 170, 1778; Mus. Calonniannni, p. 50, 



1797. Type, Area glycymeris Linnaeus. 

 Tuceta Bolten, Mus. Boltenianum, p. 172, 1798, ed. 2, p. 120, 1819. First 



species, Area pilosa Linnaeus. 

 Aaiinea+Axineoderma Poli, Test. Utr. Siciliae, vol. 1, p. 32, 1791 ; voL 2, 



p. 254, 1795 (not binomial). 

 Peetunculus Lamarck, Prodrome, p. 87, 1799. Type, Area pectunculus 



Linnaeus. — Lamy, Journ. de Conchyl., Feb., 1912, p. 84. Not of Hud- 



desford, App. to Lister Concb. Index to Anat. plates, p. 5, pi. 13, fig. 1, 



nQO.—Cardium eclule Linnaeus. 

 Glyeymeris Dall, Trans. Wagner Inst., vol. 3, pt. 4, p. 607, 1898; Proc. 



Mai. Soc. London, vol. 10, pt. 3, p. 255, 1912. Not Glyeymsris Lamarck, 



1799 or 1801. 



GLYCYMERIS LAMYI, new species. 

 Plate 20, figs. 11, 13. 



Shell small, solid, moderately convex, equivalve, and nearly equi- 

 lateral; beaks small, low, pointed, median, separated by a narrow 

 diamond-shaped area with about half a dozen ligamentary grooves 

 divaricating from a central imaginary line perpendicular to the beak 

 in each valve; external sculpture of about 20 low, slightly convex, 

 primary radiating riblets, with from one to three smaller intercalary 

 close-set threads in the interspaces ; the primary ribs extend over the 

 anterior and middle portions of the shell, but cease near the posterior 

 end, which is sculptured on the posterior area only by threads of the 

 secondary type of which there are about a dozen; these radial ribs 

 are crossed by concentric lines, sometimes rather pronounced, in 

 harmony with the lines of growth and better developed near the 

 margin; profile slightly attenuated toward the beaks and at the 

 lower end of the posterior dorsal area slightly subangular; interior 

 smooth, the margin crenulate as figured ; muscular impressions small, 

 distinct ; disk smooth ; hinge with about 10 teeth on each side of the 

 median line, symmetrically arranged. Height 16.5 mm., breadth 17.5 

 mm., diameter 8 mm. 



Tampa silex beds Ballast Point, Tampa Bay, Florida. 



Type-specimen from the Post collection. U. S. Nat. Mus. No. 

 165173. 



This form is nearest G. arctata Conrad of the Vicksburg horizon 

 in which the radial sculpture is strongest on the beaks and the coarse 

 ribs divide later, while in the present species the radials are smaller 

 on the beaks and stronger distally. The Vicksburg species is also 

 generally higher and somewhat shorter. 



