- T^Zl - 



snail er, less Gonver> speoiraens, uhich also have more prominent 

 umlDones. The lar.p-est oi '" 'ore normal she]"' ..ollow- 



vcr- di, Clio J.O..D :- I^-oi:., . .; :'1/-., ., ocrnidiam. , 10 vwx, 



-' c • lallest of fhe inordinately'" conver forms fiirnishes those 

 measurements:- lat., ?E ram., alt., 55. 5 nm., '/ '• .,15 m:'. 



Dall has fi — - ' -■-- -^"'e -----ptlj^ convex .<),l.:.. . ^^ shells 



have a decidedly different aspect heoause of their narrower and 

 ■-■fjher ujnhones, as well as because of the no'^^ehle '■" -'c in 



convexity?. The strong eonvexit- •^-" even ..ij-'-'L'.l J ' '■ "Is 



the rather fine concentric ri\q;ae are the characteristic fea- 

 trires of this species. The Tampa silex P. v/acissantis Dall (1) 



(1). loo.,--it., p* 15 65, pi. 50, fig. 15, 1905. 



is smaller, less convex with a steeper and longer anterior --^or- 

 sal mar -in. The adult P. -leraii Dall [2] from the Ohipola marl, 



(2). idem, p. 1566, pi. 50, fig. 17. 



is ^ I'Onvex, with smaller rnhoues and coarst-r nor.np-^tric 



sculpture. P. densatus Jonrad (r), r.hich occurs in ti:e OaJc 



(5). Am. Jo'zr. Oonch., vol. 5, p. 15, 1867 ( =L . pennsvlvani ca 

 Tuomey ^: Holm.es, Pleioc. IPos. 3, Gar., p. oC, pi. 18, fi 

 5, 1856; non Linnaeus). 



