TRANSACTIONS OF WAGNER 

 894 



TERTIARY FAUNA OF FLORIDA 



where forms now living in the Pacific and formerly common to both coasts 

 have become extinct in the Mexican Gulf and Antillean region. " Mactrimtla" 

 viaccscens Guppy, from his types found in the Manzanilla Eocene beds of 

 Trinidad, is also a Micromactra and related to the present species, but more 

 strongly undulated. 



Section ISIactrototiia s. s. 

 Mactra (Mactrotoma) fragilis Gmelin. 

 Plate 27, Figures 1,4, S, 18. 

 Mactra fragilis Gmelin (after Chemnitz), Syst. Nat., p. 3261, No. 22, 1792. 

 M. brasiliana Lam., An. s. Vert., v., p. 478, 181S. 

 M. oblonga Say, Journ. Acad. N. Sci. Phila., ii., p. 310, 1822. 

 M. anserina Guppy, Ann. Mag. N. Hist., xv., 1875, p. 50, pi. vii., fig. i. 



Pliocene of the Caloosahatchie beds, Dall and Willcox ; Post Pliocene of 

 Simmons Bluff, South Carolina, Burns ; living from Cape Hatteras, North 

 Carolina, to Rio Janeiro, Brazil, and probably on the west African coast, in 

 moderate depths of water. 



This species, the type of the subgenus, is widely distributed and repre- 

 sented in eastern seas by very similar though generally smaller species. It 

 was. erroneously referred to the Nicobar Islands by Chemnitz, but his figure 

 enables us to correctly identify his species with the American shell. It is the 

 M. dealbata Pult, 1803; the oblongata of Ravenel, 1834; the bilineata (C. B. 

 Ad. MS.) of Reeve, 1854, and probably the ovaliiia of Lamarck, the siliciila 

 and the anibigiia of Weinlcauff. Owing to the fragility of the shell, large 

 specimens are usually broken before being thrown up on the beach, and cabi- 

 net specimens are apt to be small. The fossil specimens sometimes attain a 

 length of eleven or twelve centimetres, which is larger than any of the recent 

 shells I have been able to examine, but the differences, which I was at first 

 inclined to think were varietal, on the examination of a large series of the 

 recent shells proved to be fully within the range of individual variation in the 

 species. The Spisula fragilis of Gray in his review of the Maclridtc of 1838 

 is not this species, but a Standella from the East Indies. 



Mactrotoma fragilis is represented in the Pacific coast fauna by the M. 

 nasnta of Gould, a distinct but allied species which was referred to by Car- 

 penter under the name ol fragilis. 



Mactra (Mactrotoma) 'Willcoxii n. s. 

 Plate 28, Figures 10, 11. 



Pliocene of the Myakka River, Florida ; Willcox. 



