FREE INSTITUTE OF SCIENCE 



747 



TERTIARY FAUNA OF FLORIDA 



nineteen to twenty-two. It has a preference for quiet water, and generally 

 attaches itself to hard substances, — coral, vermetus rock, and stones, — and has 

 a wide range of coloration, usually bright. Of the fossil specimens nine had 

 seventeen ribs ; fifteen, eighteen ribs ; seven, nineteen ribs ; four, twenty ribs ; 

 four, twenty-one ribs ; and one, twenty-two ribs ; thus showing a slight ten- 

 dency towards fewer ribs than in the recent specimens. 



Pecten gibbus var. amplicostatus Dall. 



Pliocene to recent. 



This differs from the typical giblnis by its fewer and broader ribs. It is 

 about the same size as the type, and occurs chiefly west of the Mississippi, on 

 the Texas coast, and south to Carthagena. It is usually white or nearly white 

 on the right valve, and grayish with mottlings of white on the left valve. Of 

 fourteen specimens, one had twelve ; two, fourteen ; four, fifteen ; and seven, 

 sixteen ribs. It is quite tumid and very solid, and probably inhabits coral or 

 rocky bottom. Of the fossils one had fourteen ; ten, fifteen ; and sixteen, 

 sixteen ribs. 



Pecten gibbus var. nucleus Born. 

 Ostrea nucleus Born, Test. Vind., p. 107, pi. 7, fig. 2, 1780. 

 Pecten gibbosus variegatus, etc., Chemn., Conch. Cab., vii., p. 323, pi. 65, figs. 621 a-b, 



1784. 

 Osirea titrgida Gmelin, Syst. Nat., vi., p. 3327, 1792 ; Lam., An. s. Vert., vi., p. 167, 1819 ; 



fide Hanley. 

 ? Ostrea conspersa Gmelin, p. 3320, + O.flmida Gmelin, p. 3330, + O. guttata Gmelin, 

 P- 3330. 1792. 

 Recent. 



This is a small, thin, polished form, usually variegated with gray, white, 

 and dark brown, and having twenty-one to twenty-three ribs. Its peculiarities 

 are due to the fact that it attaches itself to fuci rather than hard objects. Its 

 range extends from the Florida Keys through the Antilles. This form was 

 not found in the Caloosahatchie marls. 



Pecten gibbus var. borealis Say. 

 Pecten borealis Say, Journ. Acad. Nat. Sci. Pliila., ii., p. 260, 1822. 



Pleistocene and recent. 



This is the large, thin, dark-colored form of the New England coast, 

 ordinarily known as irradians Lamarck. It usually has fewer ribs than the 



