82 



PHYLOGENY OF FUSUS AND ITS ALLIES. 



are somewhat finer, and are to be considered as belonging to the 

 spindle. The ribs throughout are rounded, and usually distant 

 more than their width. In the later whorls they become obsolete 

 towards both sutures. Harris figures a specimen (Bull. Am Pal., 

 I, pi. i8, fig. 12) from near Oakhill, Alabama, of the variety 

 designated by him as the " Matthews' Landing-Oak Hill type." 

 in which the third spiral below the carina is strength- 

 ened, this spiral being just below the edge of the suc- 

 ceeding whorls. Intercalation occurs between the 

 primary spirals of the spindle (fig. 5). 



The variety here described characterizes the lowest 

 Eocene or Midway stage of the Gulf States. It dif- 

 fers in some respects from the type of the species as 

 figured and described by Aldrich, and later refigured 

 by Harris (fig. 4). The chief differences are, accord- 

 ing to Harris ; the greater number of costae on some 

 of the whorls in the Midway variety where they num- 

 ber as high as eighteen, while in the Lignitic variety 

 seven or eight is the usual number; and the absence of the second 

 incipient carination at the suture in the Lignitic variety, this being a 

 marked feature in the Midway variety from Matthews' Landing. 



Localities: Alabama Woods Bluff, Matthews Landing, Oak Hill, 

 Dale Branch. 



Ho}'icon: Lower Eocene, Midwayan and Chickasawan groups. 



Fig. 5. Falsi- 

 fusus meyeri, 

 Midway variety. 



FALSIFUSUS LUDOVICIANUS (Johnson). 



(Plate XVIII, fig. I.) 

 1899. Fusus ludovicianus Johnson, Proc. Phil. Acad., p. 72, pi. 4, fig. 5 



The protoconch of this species agrees in essential 

 characters with that of F. meyeri. The first two 

 whorls are smooth and gradually increase in size. The 

 next whorl is marked by oblique narrow smooth rib- 

 lets essentially as in F. meyeri. This is followed by 

 the normally round-ribbed and spirally marked whorls, 

 which with but slight modification continue to the adult 

 stage. The shoulder is slightly flattened, but there is 

 no pronounced angulation or carination of the whorl. 

 It is, however, more bulging in the center than is nor- 

 mal in rounded-whorled species of Fusoid shells. 



Locality: Louisiana, St. Maurice Winn Parish 

 (Johnson) ; Phil. Acad. — (U. S. Nat. Mus. 147226). 



Horizon: Eocene, Lower Claiborne. 



Fig. 6. Falsi- 

 fusus ludovici- 

 anus. (After 

 Johnson.) 



