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IOQ7 

 TERTIARY FAUNA OF FLORIDA 



islaiidicnin (which does not occur in the Syst. Nat.), and gives for it the 

 reference to C. pcctinatnin Linne (cf. Am. Marine Conch., p. 175). 



Like most northern shells this is very variable, but the differences are 

 inconstant. The law that the greater the number of serial parts the greater 

 the range of variation of that number in different individuals holds good in 

 this case, as usual. The original description of Fabricius calls for thirty-two 

 to thirty-eight ribs. Chemnitz allows from twenty-six to thirty-six ; C. 

 Haycsii, thirty-three to thirty-five, and C. arcticum is figured as having about 

 twenty-nine ribs. The most usual number is thirty-five, always well separated 

 from one another, and having a tendency to angularity, most marked in the 

 adult. 



Cardium (Cerastoderma) decoratum Grewingk. 



Cardium decoratum Grewingk., Verb. Min. Ges. St. Peters, for 1848-49, p. 274, pi. iv., 

 figs. 3 a-g; 1850. 



Pliocene ? of St. Paul Island, Unga Island, and Aliaska Peninsula, Alaska ; 

 Pleistocene of Kadiak and Atka Islands and Pavloff Bay, Alaska, and in 

 the bowlder clay deposits south and east to Comox and Victoria, Vancouver 

 Island. 



This is a very characteristic species of the bowlder clays of the northwest 

 coast, narrower and proportionately heavier than C. ciliatnin, showing usu- 

 ally concentric color zones when well preserved ; twenty-five to thirty-one 

 ribs, frequently reticulated by concentric elevated lines. 



Section Dinocardium Dall. 

 Cardium (Cerastoderma) phlyctaena n. sp. 



PLATE 48, FIGURE 13. 



Oligocene of the silex beds at Ballast Point, Tampa Bay, Florida ; Willcox 

 and Dall. 



Shell solid, squarish, with rather elevated beaks and convex valves ; sculp- 

 tured with thirty-one flatfish, narrow radial ribs, the anterior half of which 

 have the usual lepidote sculpture of this group, the posterior half being nearly 

 smooth and all separated by somewhat narrower channelled interspaces; pos- 

 terior area large, nearly smooth, with sparse radial grooves along which are 

 set minute distant pustular spines ; a small pseudolunule is present ; hinge 

 normal, solid, internal margin in front and below with very short flutings. Alt. 

 27, Ion. 25.5, diam. 18 mm. 



