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803 



TERTIARY FAUNA OF FLORIDA 



is a typical Crenella, and ^fyoparo is, of course, a synonyme specifically and 

 gcnerically of Conrad's form. Nncitlocardia is only a well-observed, strongly 

 crenulate Crcnclla, and what else, if anything, the undescribed Crcnellodon 

 may be is unknown. 



Crcnclla margaritacea Conrad has for a synonyme C. costata Lea; C. iso- 

 cardioidca Lea (as Hippagus) and C. latifrons Conrad (+ Modiola tennis Meyer, 

 1887) are Claibornian. The last mentioned is a large, oblique, thin species, 

 and extends into the Jacksonian. 



C. conccntrica Gabb (Pal. Cal., i., p. 186, pi. 24, fig. 169) is extremely 

 similar to C. margaritacea and is found in the Martinez Eocene of California. 

 A shell which is perhaps a Crcnclla (or a Limcea) was described from the 

 Miocene of Petersburg, Virginia, by H. C. Lea under the name of Nuctila 

 ceqitilatcra. 



Crenella divaricata Orbigny. 



iia divaricata Orb., Moll. Cubana, ii., p. 311, pi. 27, figs. 56-59, 1847 (Spanish 

 edition and atlas 1845) ; Gabb, Geol. St. Domingo, p. 252, 1873. 

 diriissata Dall, Blake Pelecypoda, p. 235, 1886. 



Oligocene of St. Domingo and Pliocene of Costa Rica, Gabb ; Pliocene 

 of the Caloosahatchie and Shell Creek, Florida, Dall and Willcox ; recent 

 from Cape Ilattcras to the West Indies (one hundred fathoms off Barbados), 

 and also on the Pacific coast at Panama and in the Gulf of California. 



This little shell is not to be distinguished, except by its nearly white 

 color, from the young of C. decussata of the same size. The examination of 

 a much larger series of specimens than was at my disposal when preparing 

 the Blake report shows that the size when fully adult is uniform and always 

 smaller than the adult C. decussata. The young divaricata is proportionately 

 less inflated and has a more circular outline than the full-grown shell. The 

 color is yellowish or nearly white in all the specimens I have seen, and the 

 epidermis hardly perceptible. 



Crenella minuscula n. s. 



PLATE 35, FIGURE 22. 



Oligocene of the lower bed at Alum Bluff, Chattahoochee River, Florida; 

 Burns. 



Shell minute, thin, inflated, elongate ovate, feebly radially striated, the 

 striations apparently diverging from a medial line on the disk ; not dichoto- 

 mous ; the beaks smooth ; inner margins crenulate; valves nearly equilateral. 

 Alt. 1.75, lat. 1.25, diam. i mm. 



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