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I l6l 



TERTIARY FAUNA OF FLORIDA 



This species recalls R. striatnla Verrill and Bush, but is larger, less dis- 

 tinctly truncate, less regular in form, and somewhat smoother and more con- 

 vex. The specimens of R. striatnla I have compared with it have, as a rule, 

 smaller and less stout dental lamellse. 



Rochefortia bidentata Montagu. 

 Mya bidentata Montagu, Test. Brit., p. 44, pi. 26, fig. 5, 1803. 

 Montacuta bidentata Turton, Dithyra Brit., p. 60, 1822 ; Forbes and Hanley, Brit. Moll., 



ii., p. 75, pi. 18, figs. 6, 6a, 1853; Jeffreys, Brit. Conch., ii., p. 208, pi. 5, fig. i, 1863; 



v., p. 177, pi. 31, fig. 8, 1869 ; not of Verrill and Bush, Proc. U. S. Nat. Mus., xx., 



p. 779, pi. 93, figs. 7, 8, pi. 94, fig. 6, 1898; not of Gould, Inv. Mass., p. 59, 1841. 

 Anatina bidentata Brown, 111. Conch. Gt. Brit., ist ed., pi. 11, figs. 8, 9, 1827. 

 Mesodesma exiguum Loven, Ind. Moll. Scand., p. 42, 1846. 

 Tellimya bidentata Brown, 111. Conch. Gt. Brit., 2d ed., p. 107, 1844; H. and A. Adams, 



Gen. Rec. Moll., ii., p. 478, 1857. 

 Erycina faba Nyst -|- E. nucleola Recluz, tide Jeffreys. 

 Mysella bidentata Dall, Synopsis Lept. N. Am., p. 890, 1899. 



Pliocene of Italy, Great Britain, and Ireland ; Pleistocene of Norway ; 

 recent from Finmark to the Mediterranean and at Madeira. 



The Montacuta bidentata of Gould, in 1841, is Aligena elez'ata Stimpson 

 (sp.) non Morch. The true R. bidentata is not known from America, the 

 shell known by that name is the following species : 



Rocliefortia planulata Stimpson. 



Plate 45, Figure 7. 



Kellia rubra Gould, Inv. Mass., p. 60 (ex parte), pi. 2, fig. 33, 1841 ; not of Turton, 



Dithyra Brit., p. 58, 1822. 

 Kellia planulata Stimpson, Shells of New England, p. 17, 1851 ; Verrill, Inv. An. Vineyard 



Sound, p. 688, pi. 30, fig. 6, 1873 ; Dall, Bull. 37, U. S. Nat. Mus., p. 48, 1889. 

 Lasaa planulata Jeffreys, Ann. Mag. Nat. Hist, Oct., 1872, p. 239. 

 Montacuta bidentata Verrill and Bush (and vars. tenuis and fragilis V. and B.), Proc. 



U. S. Nat. Mus., XX., p. 779, pi. 93, figs. 7, 8, pi. 94, fig. 6, 1898. 

 Mysella planulata Dall, Synopsis Lept. N. Am., p. 890, 1899. 



Phocene of the Caloosahatchie marls of Florida ; Pleistocene of the Gulf 

 of Maine ; recent from Massachusetts Bay to Cape Hatteras and on the coast 

 of Texas (var. fragilis) and from Wood's HoU, Massachusetts, to Cape Hat- 

 teras, North Carolina (var. tenuis). 



The variety tenuis of Verrill and Bush is distinguished from the typical 

 planulata (which is the same as their M. bidentata var. fragilis) by its larger 

 and thicker hinge laminje and usually more solid shell. These teeth vary, 



