Amrrican East Coast Arcas 



"List. Conch, t. 367. f, 207. 



"Habite les mers de la Jamaique. Mus. no. Elle est tres-baillante au bord supcrieur. 

 Largeur, 50 millimetres."— Zawa/r,^, 1819. 



Anterior and posterior are reversed in Lamarck's description. 



Ribs on the center of the shell small and rather even, larger anteriorly; posterior 

 slope wath four to six larger, more widely spaced ribs; fine ribs in some of the inter- 

 spaces, especially on the anterior part of the shell, ribs crossed by concentric raised 

 lines which give the part of the shell anterior to the umbonal ridge an imbricated nodu- 

 lar appearance; radial sculpture predominant on the posterior slope; umbonal ridge 

 usually angular; cardinal area wide with diagonal grooves; teeth numerous, nearly ver- 

 tical, smaller where the grooves cross the hinge; posterior margin nearly straight; byssal 

 opening large; shell unevenly stained with blackish or bluish brown; epidermis long and 

 scaly, chiefly about the margin and posterior slope. 



''Like all the group, this nestling species is variable in fonn according to its station, 

 but I have been unable to find any characters to separate the fossil and recent shells 

 when allowance is made for the deformations alluded to * * *. It probably retreated 

 to wanner waters during the Miocene invasion of Florida and did not succeed in return- 

 ing until the end of the Pliocene, as it has not turned up in the Caloosahatchie marls. 

 The form doubtfully identified by Professor Heilprin with A. Listen \s connected by a 

 fuller series with the others." — Dall. 



Many authors have united the Atlantic and Pacific forms under the name of A. im- 

 bricata Bruguiere. Dall placed A. Lis/eri (Tryon) Heilprin, W. F. L S. Trans., vol. i, 

 p. 113, 1887, and Barbatia Bonaczyi Gabb, Am. Phil. Soc, Trans., vol. 15, p. 254, 18 3, 

 undeT A. um'jonafa. A. amenra/ia d'Orhigny, 1846, Voyage dans I'Amerique IMerid- 

 ionale, Moll., p. 632; Hist. Isla Cuba, pt. 2, vol. 5, Moll , p. 342, vol. 8, pl. 28, figs i, 2, 

 is this species. 



Dimensions. — Lon. +14,-31; alt. + 7, -21; diam. :$ irmi- 



Occurrence. — "Oligocene of the Chipola beds, Calhoun County. Florida; of the Ballast 

 Point Silex beds, Tampa Bay, Florida; of the Alum Bluff sands at Oak Grove, Santa 

 Rosa County, Florida. Also in the Pleistocene of the Florida Keys and the Antilles, 

 and living from Cape Hatteras, North Carolina, south to Santa Caterina, Brazil, and 

 throughout the Antilles." — Dall. Oligocene of Bailey's Ferry, Florida, and recent from 

 Florida, Galveston, Texas, the West Indies, Aspinwall and Brazil. — C. U. Museum. 



Area wagneriana Dall 

 Plate I, Figures 18, 19 



Area (Arcoptcra) aviculafottnis Heilprin, Wagner Free Inst. Sci., Trans., vol. i, p. 98, pl. 13, 



figs. 32, 32a, 1887. 

 Not Area aviculaformis Nyst, Tabl , Synopt., p. 12, 1S48; Area aviculoides 'Reeve, i!ii44.^de Dall; 



not A. ainculoides de Koninck, Des. An. Fos., p. 114, 1844. 

 Areofilera aviculeeformis Dana. Man. Geol., 4th ed., p. 900, fig. 1510, 1895, 

 Area Wagneriana Dall, Wagner Free Inst, Sci., Trans., vol. 3, pt. 4, p. 619, 1898; pt. 5, pl. 39, 



figs. 6, 7, 1900. 



