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995 



TERTIARY FAUNA OF FLORIDA 



a miniature Cytherea, and by its very fine, close, concentric striation. In the 

 latter feature it surpasses the Oak Grove 5". nuculoidea var. striulata, which 

 in its turn is more finely sculptured than the Miocene type, but the striulata 

 is not intermediate in form, being more elongated and parallel-sided than 

 either its ancestor or its descendant, if we may so term the Chipola and Duplin 

 species respectively. The -S\ cythcreoidca is also on the whole a smaller species 

 than either of the others mentioned, the largest specimens among a large 

 number measuring five millimetres long by 3.75 high and having a diameter 

 of 1.7 mm. These differential characters with the figure will serve better to 

 define the present species than a more elaborate description, which would 

 merely recapitulate for the most part the characters of 5". nuculoidea. 



The Syndosinya nucnloides of Whitfield (Mon. Mio. N. J., p. 81, pi. xv., 

 figs. 7-9, 1894) is not Conrad's species, nor does it belong to this genus; the 

 specimen is an undoubted Sportella of the section Fabella Conrad.. 



The Amphidesma transversa of Say (Am. Conch., iii., 28, 1831) is not an 

 American shell, the species being based on a specimen of Scrobicularia piperita 

 which Mr. Say had been led to suppose indigenous. What the species de- 

 scribed by Holmes under the same name (Post-Pi. Fos. S. Car., p. 52, pi. 

 viii., fig. 10) may be, neither his description nor his figure is sufficient to 

 determine. The Amphidesma lepida Say is a Lepton and his A. punctata is 

 a Diplodonta. A. constricta Conrad is a Fabella, as is his A. protexta. A. 

 inequale " Say" Conrad (Journ. Acad. Nat. Sci. Phila., vii., 153, 1834) is a 

 lapsus for A. (Abra) cequalis Say. 



On the Pacific coast Semele decisa Conrad, and S. pulchra Sowerby, are 

 reported by Gabb from the Pleistocene of California (Pal. Cal., ii., p. 94, 

 1869). 



Genus ABRA (Leach) Lamarck. 



Abra (Leach MS.) Lam., An. s. Vert., v., p. 492 (in synonymy), 1818. First species 



Mactra tenuis Mont. 



Amphidesma (sp.) Lam., op. cit., p. 492, 1818; Leach, Moll. Gt. Brit., p. 278, 1852. 

 Ligula (sp.) Montagu, Test. Brit., Suppl., p. 96, 1808; not of Humphrey, 1797, nor Bloch, 



1782. 



Abra Gray, Ann. Mag. N. Hist., xx., p. 272, 1847. 

 Syndosmya Recluz, Rev. Zool., 1843, pp. 292, 359. Type Amphidesma Boysii Lam., = 



Mactra alba Wood. 



Syndcsmia (corr.) Chenu, Agassiz, 1846. 

 Orixa Leach, Moll. Gt. Brit., p. 280, 1852. Type Mactra tenuis Montagu ; Fischer, Man. 



de Conchyl., p. 1152, 1887. 



