1907.] NATURAL SCIENCES OF rHILADELPHIA, 215 



of the great strcngthoiiiiip; of its primary spirals. In this respect it 

 resembles the Panamic P. dccussata. The imspecialized apex of 

 P. dccussata is, however, sufficient to prechide a derivation from this 

 fossil Santo Domingan form. Altogether this latter appears to be 

 an early departure from the stock of the generalized Pyrulas of the 

 Oligocene and Miocene. It probably has no descendants in later beds. 

 I have referred it with some doubt to Pyrula carbasca Guppy.*° 



Table III shows that the apex was as variable in the Eocene, Oligo- 

 cene, and Miocene as at the present day. The great length of the 

 smooth stage and slight acceleration of the cancellated stage are note- 

 worlliy features of this group of species. It is only in P. carhasea(?) 

 that the smooth stage is short and restricted. 



Range and Distribution. 



The genus Pyrula as restricted in this paper ranges from the late 

 Eocene to the present day. Earlier in the Eocene we encounter an 

 abundance of forms which appear to be closely related to the species 

 here considered. Their inclusion in the present study would, it is 

 believed, throw some doubt on the nionoi)hylctic nature of the group. 

 Their consideration is therefore delayed, so that wc may be able to 

 observe the changes in a series which obviously can be referred to 

 only one generic stock. 



In the Jackson Eocene and in the later Vicksburg beds the species 

 are remarkable for the great length of the smooth stage and for the 

 small size of the earl}' whorls. The same cliaracteristics are also to be 

 observed in the European Miocene Pyrula condita. The three species 

 P. filia of the Jackson Eocene, P. niississippicnsis of the Mcksburg 

 beds, and P. condita of the ]\Iioccne of Europe all (>x]iil)it similar apical 

 features. They represent the most primiti\-o expression of the Pyrula 

 assemblage which the geological record furnishes. 



In the Oligocene (or Miocene) deposits of Bowden, Jamaica, we find 

 Pyrula pUsbryi, and in the Miocene of Xortli Carolina occurs P. pilsbryl 

 duplincnsis. Both are very much alike as to the characters of the 

 smooth stage. In them it is more restricted than in P. condita or in 

 the American Vicksburg and Jackson types. In other words, the 

 cancellated stage is thrown farther back into the ontogeny. In addi- 

 tion, the early whorls have now become larger in size. Altogether P. 

 pilsbryi is very similar in its early whorls to P. dccussata, P. dussumicri, 

 P. ficus, and some specimens of P. reticulata. These three latter species 



^^Ficula carbasea Q. J. Geol. Soc. Land., 1S6G, Vol. 22, p. 580. 



