TRANSACTIONS OF WAGNER 



TERTIARY FAUNA OF FLORIDA 



Subgenus Cyathodonta Conrad. Type T. undulata Conrad. 



Shell resembling Thracia but with a sculpture of strong oblique ripples ; 

 hinge-plate not fissured, but continuous ; beaks entire ; the resiliifers short, 

 rounded, prominent, with a thin, semicircular, vertically pendant lithodesma 

 in front of them. 



The genus recedes in time to the Trias, and for the Mesozoic species Agas- 

 siz proposed the genus Cory my a, which, however, is regarded by Zittel as not 

 distinct from Thracia. The Tertiary species are not abundant and, owing to 

 the delicate structure of the shell, are rarely well preserved. Cyathodonta is 

 well developed in the Oligocene, species appearing in the Vicksburgian and 

 Antillean beds as well as in those near Bordeaux, France. It is represented by 

 a few species in the existing fauna, which in accordance with its geological 

 antiquity are widely distributed in Africa, the Indo-Pacific, California, and the 

 Caribbean waters. 



Thracia Dilleri Dall. 

 PLATE 34, FIGURE 19. 

 Thracia Dilleri Dall, Trans. Wagner Inst., iii., p. 929, pi. xxxiv., fig. 19, 1898. 



Middle Eocene of the Arago beds, near Cape Arago, Coos County, Oregon ; 

 J. S. Diller, United States Geological Survey. 



Shell of moderate size, thin, elongated, inequilateral, nearly equivalve, mod- 

 erately convex ; anterior side shorter, surface concentrically feebly undulated, 

 slightly granulose as usual in the genus ; basal margin somewhat flexuous, an 

 obscure ridge running to the middle of the base and another to the basal pos- 

 terior angle in the left valve, a marked carina extending from the beaks near 

 and almost parallel to the dorsal margin, the space between the margin and 

 the carina wider in the right valve ; posterior end subtruncate, produced, beaks 

 adjacent, inconspicuous. Alt. 30, Ion. 48, diam. i6lrim. 



This species is sufficiently distinguished by its elongated form from any 

 of the other species of the genus in the Pacific coast Tertiaries. 



Thracia Oonradi Couthouy. 



Thracia Conradi Couthouy, Boston Journ. Nat. Hist., ii., p. 183, pi. iv., fig. 2, 1838; Am. 



Journ. Conch., iv., App., p. 54, 1868; Dall, Bull. U. S. Nat. Mus. No. 37, p. 64, pi. 



Ixix., fig. 9, 1889. 

 Anatina convexa Greene, Mass. Cat., 1833; not of Turton. 



