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TERTIARY FAUNA OF FLORIDA 



cardinal bifid; an elongate anterior lateral corrugated on both sides and re- 

 ceived into a corrugated pit in the right valve ; nymphs plain. 



This form, while less orbicular, recalls Dosiniopsis and Cyclorisma by its 

 characters, differing from the former by the absence of granulations on the 

 nymphs and of a posterior lateral tooth,- and from the latter by the presence of 

 a defined lunule and an anterior lateral tooth. 



It is a member of the upper Cretaceous fauna of the southeastern United 

 States. 



Subgenus ANTIGONA Schumacher. 



Type Cytherea lamellaris Schumacher (Dosina lamarckii Gray). 



Shell smaller and more trigonal, less rotund than Cytherea s. s. ; the left 

 anterior lateral lamelliform and larger, with a perceptible socket in the right 

 valve ; the posterior right cardinal broad and deeply bifid ; pallial sinus small, 

 triangular. 



Section Antigona s. s. 



Shell rather elongate, with profuse concentric lamellae crenulated by fine 

 radial ribs; the lunule deeply impressed, the ligament exposed, the overlap 



of the escutcheon small. 



X 



Section Artena^ Conrad. 



Shell trigonal or short, with acute concentric laminae, between which are 

 minute elevated concentric lines ; lunule not deep ; escutcheon x large, not over- 

 lapping; posterior right cardinal narrow; anterior left lateral compressed, 

 narrow, laminar ; other features as in Antigona. 



This section bears to Antigona much such a relation as Ventricola does to 

 typical Cytherea in the other subgenus. 



/ 



Subgenus CIRCOMPHALUS Morch. 



Circomphalus (sp.) Herrmannsen, Ind. gen. Mai., i., p. 237, 1847; Morch, Cat. Yoldi, p. 



23, 1853 ; H. and A. Adams, Gen. Rec. Moll., ii., p. 422, 1857. No type selected. 

 Circumphalus Tryon, Syst. Conch., Hi., p. 176, 1884; V. plicata Gmelin (= V. dysera 



Linne, pro parte). 

 Anaitis Tryon, Syst. Conch., iii., p. 177, 1884; not of Duponchel, Lepidoptera, 1829, nor 



of Romer, 1857 {ex parte). 

 Chiona Romer, Krit. Unters., p. 16, 1857 ; not of Morch, Cat. Yoldi, p. 24, 1853. 



Shell cordate, compressed, with distant elevated reflected laminae, more or 

 less phyllate near the escutcheon ; lunule and escutcheon impressed, sharply 



