118 BULLETIN 00, UNITED STATES NATIONAL MUSEUM. 



Family ARCIDAE. 



Subfamily .AJRCINAE. 



Genus ARCA (Linnaeus) Lamarck. 



Area Linnaeus, Syst. Nat., ed. 10, p. 693, 1758. — Lamarck, Prodrome, p. 87, 



1799. Type, Area noae Linnaeus. 

 Area Dall, Trans. Wagner Inst., vol. 3, pt. 4, p. 613, 1898. 



ARCA UMBONATA Lamarck. 

 Plate 17, figs. 6, 8. 



Area umhonata LAMARdK, An. s. Vert., ed. 2, vol. 6, p. 37, 1S19. — Deshayes, 

 vol. 6, p. 432, 1835 (Si/n. part, cxelus.). — Philippi, Abb. und Beschr., 

 vol. 3, p. 13, pi. 17&, figs. Sa-c, 1847.— Dale, Trans. Wagner Inst., vol. 3, 

 pt. 4, p. 620, pi. 38, figs. 4, 4o, 1898. 



A7'ca noae Stimpson, Smith lust., Clieckl. E. Am. Marine Shells, p. 2, 1860; 

 not of Linnaeus. 



Area imbricata Heilpkin, Trans. Wagner Inst., vol. 1, p. 118, 1887. 



Area listeri Heilprin, Trans. Wagner lust., vol. 1, p. 118, 1887, after Tryon. 



Barhatia honaczyi Gabb, Geol. Santo Domingo, p. 254, 1873. 



Oligocene of the Tampa silex beds at Ballast Point, Tampa Bay ; 

 of the Chipola marls, Calhoun Coimty ; and of the Oak Grove sands, 

 Santa Rosa County, Florida. Pleistocene of south Florida and the 

 Keys. Living from the vicinity of Cape Hatteras, North Carolina, 

 south to Brazil and throughout the Antilles. U. S. Nat. Mus. No. 

 165174. 



This is a very widespread species, both in time and in geographical 

 distribution at the present day. It seems to have retreated from 

 Florida waters to warmer regions during the Miocene and returned 

 there about the end of the Pliocene epoch. 



ARCA GRAMMATODONTA, new species. 



Plate 20, figs. 1, 2 ; plate 22, fig. 3. 



Shell resembling Area faratina., but more inflated, relatively 

 wider, with the anterior end of the shell projecting before the angle 

 where the hinge line ends, and with the latter rounded off; the pos- 

 terior angle is similarly less conspicuous and the posterior trunca- 

 tion of A. paratiTui is replaced by a rounded-lanceolate profile; the 

 area of the present species is relatively wider, and the triangle 

 formed by the resiliary grooves is shorter and more equilateral; 

 the anterior radial sculpture is alternated, the stronger ribs con- 

 spicuously beaded, while in A. imratina they are nearly plain, and a 

 similar difference characterizes all the radial sculpture; the most 

 marked difference occurs in the hinge teeth, which in the present 

 species are sharply grooved vertically, while the teeth of A. paratina 



