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1430 



TERTIARY FAUNA OF FLORIDA 



however, a more larval type of hinge with a straight hinge-line and crenulate 

 provinculum not unlike that of Lim&a. 



It is named in honor of the lamented F. Bernard, whose researches on the 

 development of the bivalve hinge have been so fruitful. 



Superfamily CYRENACEA. 



FAMILY CYRENID^E. 



Hinge when fully developed having three cardinal teeth in each valve ; in 

 the fossil precursors some of these may be suppressed. 



This family was called Corbiculidce by Prime, and there is much to be said 

 in favor of retaining his name, as Corbicula is the most prolific in species and 

 has a larger number of allied groups than Cyrena, though the latter possesses 

 the largest individuals, and Gray used the name Cyrenidce in 1840. 



This family is first differentiated in the Mesozoic and includes the following 

 groups : 



Genus Cyrena Lamarck, 1818. 

 Genus Corbicula Megerle, 1811. 

 Genus Miodontopsis Dall, 1903. 



Valves subtrigonal, with two cardinals and two long, cross-striated laterals 

 in each valve, the anterior and posterior laterals subequal; pallial line with a 

 small sinus. 



This is Miodon Sandberger,* 1870, not of Carpenter, 1865. The type is 

 Cyrena media Sowerby, from the Upper Jurassic Purbeck beds. 



Genus Loxoptychodon Sandberger, 1872. Type Cyrena intermedia Deshayes. 



Lower Eocene. 



Valves subtrigonal, the anterior end shorter; right valve with three acute 

 triangular cardinals, the middle one bifid ; left valve with two, the larger one 

 bifid ; lateral teeth cross-striated, the anterior shorter ; pallial line with a broad, 

 shallow sinuosity; margins smooth. 

 Genus Plesiastarte Fischer, 1887. Type P. crenulata Deshayes, as Cyrena. 



Lower Parisian Eocene. 

 Shell small, subtrigonal, concentrically striated, with three cardinal teeth 



* Land u. Siissw. Conch, d. Vorwelt, 1870-1875. I know these genera of Sandberger 

 only from figures and descriptions. 



