J '■*<'"•] NATURAL SCIEXCES OF PHI LADKI-I'III A . 210 



(3) In this particular grou}) of species the differences in tlie apical 

 characters cannot be used for the division of the assemblage into 

 separate genera," but are of use only as aids to specific discrimination, 

 and then only when the characters of the later whorls are considered 

 together with those of the apex. 



Explanation of Plate XVII. 



Fig. 1. — Apex of Pijrula papyratia Say. Recent. Lee County, Fla, Shows 



the smooth stage restricted to the large and swollen first whorl. The can- 

 cellated stage starts with the beginning of the second whorl. Greatest 



diameter = 3.2 mm. 

 Fig. 2. — Apex of Pyrula papyratia cahosahatchiensis. Pliocene. Caloosahatchie 



River, Fla. Here the cancellated stage is hardly as accelerated as in fig. 1. 



Greatest diameter = 3.2 mm. 

 Fig. 3. — Apex of Pyrula pilsbryi dupUnensis. Miocene. Duplin County, N. C. 



The smooth stage occupies about 1.5 whorls. Here the initial whorl is 



smaller than in figs. 1 and 2. 

 P^ig. 4. — Apex of Pyrula pilsbryi n. s. Oligocene (or Miocene). Bowden, 



Jamaica. Smooth stage occupying about 1.75 whorls. Greatest diameter 



= 3 mm. 

 Fig. 5. — Apex of Pyrula mississippiensis Con. Oligocene. Vicksburg Beds, 



Vicksburg, Miss. Here the initial whorl is much smaller than in P. pilsbryi 



and the smooth stage extends over three whorls. Greatest diameter = 3.5 



mm. 

 Fig. 6. — Apex of Pyrula filia Meyer. Eocene. .Jackson Beds, Jackson, Miss. 



Smooth stage of about 2.5 whorls. Greatest diameter = 3.5 mm. 

 Fig. 7. — Apex of Pyrula decussata Wood. Recent. Acapulco. Smooth stage 



of about 2 whorls. Greatest diameter = 2.8 mm. 

 Fig. 8. — Apex of Pyrula dussumieri Valenc. Recent. China. Smooth stage of 



about 1.6 whorls. Greatest diameter = 3 mm. 

 Fig. 9. — Apex of Pyrula ficus Linn. Recent. East Indies. Smooth stage of 



about 1.7 whorls. Greatest diameter = 2.6 mm. 



" See Proc. Linn. Soc. New South Wales, 1905, Pt. II, p. 325, "Notes on Proso- 

 brancliiata. No. IV — The Ontogenetic Stages represented by the Gastropod 

 Protoconch," by H. Leighton Kesteven. On p. 334 he saj's: "The protoconch is 

 to be used in conjunction -vNith other features, and that only wliere the other 

 features, anatomic or conchological, are negative or unkno\vn is it to be used in 

 deciding a systematic position or generic segregation." 



