PIIILOGENY OF FUSUS AND ITS ALLIES. 9I 



ture and general form approach closely Fusiis closter from the West 

 Indies, except that the species is somewhat less stout. There is some 

 variation, however, in the proportional length and slenderness of the 

 spire in H. exilis. 



The young of this species agrees well with H. caloosaensis, while 

 the later whorls are more advanced than any in that species. (Advance 

 is not used here in the sense of progression, for the change is in reality 

 a degeneration. There is, however, an advance along the path followed 

 by these species in their development, both ontogenetic and phylo- 

 genetic.) 



Locality: Alum Bluff, upper beds Florida (Nat. Mus. 97493). 



Horizon: Miocene (Transition Oligocene to Miocene, Dall). 



HEILPRINIA TIMESSA (Dall). 



1889. Fiisiis timessiis Dall, Blake Moll, vol. 2, p. 166. 



1890. Fitsiis timessiis Dall, Tert. Faun. Florida, pt. i, pi. 7, fig. 6. 



This shell in its spire agrees most closely wath H. exilis from Alum 

 Bluff" (upper bed), Florida. It has, however, the contracted aperture 

 in the adult, which marks the stout variety of H. caloosaensis, but this 

 is much less marked in the young. The protoconch is of the same 

 type. It is solid, as showai by broken specimens. The bicarinate 

 aspect of the early whorls is strongly marked from the beginning, 

 owing to a covering up of the third spiral. The whorls have a some- 

 what more rounded aspect, as in the later stages of H. exilis. The 

 ribs are strong, in some specimens even bulging. They die out toward 

 the end of the fifth volution, after which there are only faint undula- 

 tions. The spirals are very sharp ; secondary spirals appear toward the 

 end of the ribbed whorl. 



The character of the sculpture of the adult is like that of H. exilis. 

 An immature H. fiiiiessiis superposed on an H. exilis of about the same 

 age shows only a slightly more contracted lip in the former — the dif- 

 ference is not so great as is that between the two varieties of H. 

 caloosaensis. 



H. exilis and not //. caloosaensis appears to represent the ancestral 

 form of H. timessiis. The species has changed very slightly since the 

 time of the Alum Bluff beds. The remarkable contraction near the 

 beginning of the anterior canal, which is so like that of H. caloosaensis, 

 is in both cases probably a senile characteristic, as suggested to the 

 writer by Dr. Dall. 



Localities: Station 2316, Gulf of Mexico, 50 fathoms on coral, temp. 

 74 degr. Off Key West (U. S. Fish Com. Nat. Mus, 93652) 

 Station 2134, 254 fathoms on sand, south of Cuba (Nat. Mus. 93653) 

 Station 2404. Gulf of Mexico, 60 fathoms on sand, between Mississippi 

 delta and Cedar Keys (Nat. Mus. 83495); Station 241 1. Gulf of 



