1907.] NATURAL SCIENCES OF PHILADELPHIA. 211 



Tabic I gives a representation of the ontogenetic features of the 

 recent species. Pyrula decussata Wood and Pyrula ficus Linn, are the 

 most clear-cut and distinctive species as regards the ornamentation 

 in the cancellated stage. Pyrula decussata is distinguished by its 

 strong primary spirals, while P. ficus has flat, weak spirals and very 

 faint ribs. Pyrula dussumicri Valenc. is^markcd by its long slender 

 form and the relatively high spire. In their apical features Pyrula 

 decussata, P. ficus and P. dussumieri are all very much alike. The 

 smooth stage occupies about 1.6-2 whorls and these early whorls are 

 small. 



Among the forms commonly grouped as Pyrula reticulata Lam. there 

 is much variation. How much of this is individual and how much 

 racial or specific it is impossible to say with the present data. They 

 all have relatively strong ribbing, and this together with spirals of about 

 the same strength gives them a much more conspicuously cancellated 

 appearance than is seen in any other recent species. 1\\ this Pyrula 

 reticulata assemblage the smooth stage occupies from 1.3 to 1.75 

 whorls and the first whorl varies not a little in size. These forms 

 strongly recall Pyrula condita Brongniart^ of the European Miocene 

 in the sculpture of the cancellated stage. It is probable that more 

 accurate collections will necessitate the division of P. reticulata into 

 separate geographical races or species. 



Pyrula tessellata Kobelt is a small type which differs from all others 

 in the peculiar character of its apex. The cancellated stage has been 

 thrown so far back in the ontogeny that little more than the globular 

 beginning of the fii'st whorl is smooth. This smooth portion is large 

 and swollen. In fact P. tessellata is, in its apical characters, the most 

 abnormal of any of the Pyrulas. 



On comparing Pyrula papijratia Say with the other species we find 

 that it is essentially similar to them as regards its cancellated stage. 

 When, however, the apex is examined it is seen to be sharply distinguish- 

 able from all other recent forms. The smooth stage is restricted to 

 about one whorl and this whorl is large and swollen. In this respect 

 P. papyratia is only surpassed by P. tessellata.- 



Table I demonstrates clearly that we may have living at one time 

 on the earth's surface a number of very closely related forms which 

 show markedly different degrees of acceleration and much variation 

 in the apex. 



Table II illustrates the changes shown by some of the American 



' See Cossmann, Essais de Pal6oconchologie Comparee, pt. V, pi. VI, fig. 7. 



