•TRANSACTIONS OF WAGNER 



794 



TERTIARY FAUNA OF FLORIDA 



Modiolus (Brachydoiites) grammatus n. s. 

 Plate 30, Figure 2. 



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

 and (var. airhibis Dall) of the lower bed at Alum Bluff, Chattahoochee River, 

 Florida, Burns. 



Shell small, thin, slender, delicately dichotomously radially ribbed ; 

 anterior end extremely short, barely exceeding the beaks ; posterior margin 

 angulated ; front margin nearly straight, basal end rounded ; inner margin 

 delicately crenulate. Alt. 20, max. lat. 8.5, diam. 6.5 mm. 



This is closely related to the recent M. citrimis Bolt., but is more attenu- 

 ated towards the beaks, and has the dorsal angulation and crenulations of the 

 margin less pronounced. The variety, which more abundant material might 

 show to be a distinct species, is stouter, more triangular, with coarser and 

 more nodulous ribs and stronger crenulations of the margin. Alt. 12, max. 



lat. 7, diam. 6 mm. 



« 



Modiolus (Brachydoiites) Gruppyi n. s. 

 Plate 35, Figure 16. 



Oligocene of the Bowden beds, Jamaica ; Henderson and Simpson. 



Shell small, thin, delicate, radiately numerously ribbed, the ribs but 

 seldom dichotomous, general form as in M. grmmnatiis, but shorter and more 

 rounded, the surface frequently concentrically faintly undulated, inner dorsal 

 margin sharply crenulate, the rest of the shell margin almost smooth ; basal 

 end of valve rounded, dorsal angle obsolete. Alt. 8.5, max. lat. 4.7, diam. 

 2.5 mm. 



This differs from the last in its more delicate and less dichotomous 

 ribbing, its more rounded, thinner, and less angular shell, and in the absence 

 of crenulations over most of the margin, due to the feebleness of the sculpture. 



Modiolus (Brachydontes) demissus Dillwyn. 

 Mytilus demissus (Solander MS.) Dillwyn, Descr. Cat. Rec. Shells, i., p. 314, 1817 ; Say, 



Journ. Acad. Nat. Sci. Phila., ii., p. 265, 1822 ; Wood, Ind. Test., p. 25, pi. 12, fig. 



30, 1825 ; Greene, Mass. Cat., 1833 ; Ravenel, Cat., p. 7, 1837. 

 Modiola pUcatula Lam., An. s. Vert., vi., p. 113, 1819; ed. Desh., viL, p. 22, 1835; 



Totten, N. Engl. Cat., 1833 ; Gould, ist Rep. Geol. Me., p. 119, 1837 ; Inv. Mass., 



p. 125, fig. 81, 1841 ; De Kay, Nat. Hist. N. Y., Moll., p. 184, pi. 24, fig. 258, 1843 ; 



Verrill, Inv. An. Vineyard Sound, p. 693, pi. 31, fig. 238, 1S73 ; Dall, Bull. U. S. 



Nat. Mus., No. 37, p. 38, pi. 54, fig. i, 1889. 



