214 PROCEEDINGS OF THE ACADEMY OF [MaV, 



introduced between the primary spirals. Other still finer spirals are 

 introduced with the progress of the ontogeny. The primary spirals 

 are the strongest, while those sets of spirals introduced latest are 

 weakest. 



Remarks. — P. pilshryi is much like the Duplin form in its apical 

 features, but differs from it in the relatively weaker primary spirals 

 which do not dominate the later intercalated spirals to any great 

 extent. For the North Carolina form the name Pyrula pilshryi dup- 

 linensis is here proposed. 



The Vicksburg species Pyrula mississippiensis Conrad,^ it will be 

 noticed, has the first three whorls occupied by the smooth stage. The 

 first whorl is also smaller than in P. pilshryi. 



In the Jackson Eocene a species, probably Pyrula filia Meyer,' has, 

 like the Vicksburg form, a small first whorl and the smooth stage takes 

 up at least 2.5 whorls. It is a little more accelerated than the later 

 Vicksburg species. This emphasizes the fact that a less accelerated 

 and specialized race does not always underlie the more specialized 

 race. 



Nevertheless we can say that on the whole Table II shows us a 

 gradual acceleration of the features of the cancellated stage as we 

 trace the different types from the Eocene to the present day. This 

 acceleration is accompanied by a gradual enlargement of the first 

 whorl until we reach the culmination of this feature in the recent 

 Pyrula papyratia. 



Another exception to this gradual development is furnished by the 

 form from the Santo Domingo Oligocene (or Miocene) which Gab!) 

 referred to Pyrula 'mississippie7isis. This reference^ is entirely incor- 

 rect, for Gabb's specimen has a very large swollen apex with not more 

 than one smooth whorl. It is fully as accelerated as P. papyratia in 

 this respect, but it cannot be ancestral to the recent species on account 



' See Ficus mississippiensis Con., J. Acad. Nat. Sci. Phila., 2d ser., Vol. 1, p. 

 117. 



* Bericht ilber Senckenbergische nafnrforschende Gesellschaft in Frankfurt a. M ., 

 1887, Ficula filia Meyer, p. 8, Taf. I, fig. 10. I make this reference -mth some 

 doubt. 



' See Gabb, in Trans. Am. Phil. Soc, Vol. 15, p. 223. Gabb considered 

 Guppy's Ficula carbasea as a synonym for Conrad's Ficus 7nississippie7isis. He 

 says: "I have compared Mr. Guppy's shell with Mr. Conrad's original specimens 

 from Vicksburg, Mississippi, and find them identical in form and sculpture. I 

 am by no means sure that this should not be considered the same as F, decussatus 

 {F. ventricosus) , the common west coast Mexican form." 



It can, of course, be neither P. mississippiensis nor P. decussata, and as it 

 resembles Guppy's figure I have referred it to P. carbasea. Guppy's type I have 

 not seen. 



