PIIYLOGRXY OF FUSUS AND ITS ALLIES. 83 



FALSIFUSUS (?) HOUSTONENSIS (Johnson). 



1899. FitsHS luuistoiiciisis Johnson, Proc. Phil. Acad. Sci., p. 72, pi. i, fig. 4. 



The apex of the only s])ecinien of this species known is imperfect, 

 and hence the precise generic position is not known. It may be a 

 true Falsifusits, tliough judg'ing' from the similarity of the shell in 

 the characters of the whorls to "Fiisits" apicalis Johnson, it is not un- 

 likely that these two species may be ,c^enerically related to each other, 

 while they may prove sufficiently distinct from FaJsifiisus to demand 

 a separate generic designation. 



The whorls of the adult shell are uniformly rounded, wath round 

 and strong ribs which reach from suture to suture, and 

 are separated by strong interspaces. The spirals are 

 simple except in the last whorl, where intercalations 

 appear between the three primary spirals. No carina- 

 tion occurs, the whorls being throughout round. John- 

 son, however, states that the whorls arc somewhat 

 angular near the apex. 



If this species proves to be congeneric with F. 

 meyeri we have a case of a species less specialized ap- 

 pearing in time after a more highly specialized one. 

 For in F. (?) honstonensis the primitive feature of 

 round wdiorls and round continuous ribs, with spirals F^. 7. Falsi- 

 mostly simple still persist, while in F. meyeri that stage /"•^"■^ (• ) "ous- 

 is long past, although it appears earlier in the Eocene j*^ , \ 

 than does F.f honstonensis. If, on the other hand, this 

 species and "Fiisus" apicalis are congeneric as appears to be the case, 

 then we can explain the apparent anomaly on the supposition that these 

 two species represent a lateral branch from Falsifusiis, in which the 

 apical whorls are more accelerated, and the conch more retarded than 

 in F. meyeri. 



Locality: Alabama Blufif, Trinity River, Houston County, Texas. 



Horizon: Lower Claiborne. 



FALSIFUSUS (?) APICALIS (Johnson). 

 (Plate XVIII, fig. 2.) 

 1899. Fusus apicalis Johnson, Proc. Phil. Acad. Nat. Sci., p. 71, pi. i, fig. 3. 



This species is referred to Falsifusiis with considerable reserva- 

 tion. Its apical whorls are so much further advanced than those of 

 Falsifusiis meyeri and similar species that a generic separation seems 

 very desirable. Nevertheless it may be best to regard this species and 

 the preceding one with it. if it prove of the same type, as a highly 

 accelerated lateral branch from F. meyeri. 



Apical whorls accelerated. The first smooth, the succeeding three 

 with fine oblique and slightly concave, smooth and closely crowded 

 riblets, which at the end of the fourth vcilution (|uickly give way to the 



