TRANSACTIONS OF WAGNER 

 1280 



TERTIARY FAUNA OF FLORIDA 



Genus SAXIDOMUS Conrad. 



Saxidomus Conrad, Journ. Acad. Nat. Sci. Phila., vii., p. 249, 1837 ; S. Nuttallii Conrad ; 



H. and A. Adams, Gen. Rec. Moll., ii., p. 437, 1857 ; Carpenter, P. Z. S., 1856, p. 215 ; 



Rep. Brit. Assoc. for 1856, p. 192 et seq., 1857; Suppl. Rep. Brit. Assoc. for 1863, p. 



641, 1864; Gabb, Pal. Cal., ii., pp. 58, 98, 1869; Dunker, Ind. Moll. Mar. Japon., p. 



208, 1182; Tryon, Syst. Conch., iii., p. 175, 1884; Fischer, Man. de Conchyl., p. 1086, 



1887. 



Venus (sp.) Philippi, Abb. und Beschr., ii., p. 151, 1846. 

 Tapes (sp.) Gould, Rep. Pac. R. R. Expl., v., p. 333, 1856. 

 Saxidomus (pars) Deshayes, Cat. Conch. Brit. Mus., i., p. 186, 1853 (Tapes sp. exclus.). 



This genus has never been correctly described or clearly understood. The 

 'animal has long, large siphons closely united nearly to their orifices, which 

 have inconspicuously papillose openings ; the margin of the mantle is slightly 

 festooned rather than fringed ; the foot is very large, triangular, with no 

 " heel," but with a compressed thin margination ; there are four rather large 

 plicate palpi; the gills are normal, rounded in front and behind, the 

 leaves subequal, and rather small for the size of the animal ; the mantle is 

 open ventrally, as in most Venerida. In harmony with these Meretricine 

 characters we find the dental formula, when correctly stated, to be L - I ? 1010 - 010 . 



R. oioioi.ioi 



The teeth are much concentrated, so that the left anterior lateral has the 

 appearance of being one of the cardinal series and the anterior right cardinal 

 is frequently in line with the adjacent lateral, so that they have been taken 

 to be one and the same tooth. The posterior right cardinal is deeply bifid, 

 the other teeth are entire and smooth. The ligament is long, strong, and wholly 

 external. There is no circumscribed or impressed lunular area or escutcheon. 

 The internal margins of the valves are smooth, the pallial line with a deep, 

 nearly horizontal sinus, rounded in front. The external sculpture is wholly 

 concentric, though the ridges of the rougher species sometimes inosculate. The 

 radially sulcate series (Saxidomus II.) of Deshayes contains only species of 

 Protothaca. The genus reaches back to the Eocene in time, the species are 

 distributed on the Asiatic and American shores of the Pacific, and their 

 metropolis is on the west coast of America. 



Saxidomus Nuttallii Conrad, 1837, was an adolescent specimen of the species 

 described by Gould in 1861 as S. aratus, and by Philippi in 1846 as Venus 

 ma.vimits (Anton MS.). The very young smooth stage was named Tapes 

 gracilis by Gould in 1855. It has in the adult state a concentrically more 

 or less sulcate surface and one or more purple patches on the dorsal mar- 

 gin. According to Cooper it occurs in the Miocene, Pliocene, and Quar- 



