- 147 - 



specimen, '^o ..iJi- i-emov - " 



'- . I ' ' - ... SGUlp- 



tiijTe, "but i-S sli.-b-'-l;/ less elon<j'ate, i^li^'-l:-!:!;^ more , ^'ith 



t]:e e^rve of the ^ ■■'^liiji c.:: less coi, v ^^^ , i-l^iicr .- '.c creot 



iimbones; all these differences are, however, vexj sli i 



even if it is desiralDle to differentiate it the nane ' .ve 



no more than varietal rank. 



Dall (l) has commented on the -progressive weahen: 



(i). loo. Git., 



^harsctc-ristic scril"Dtirre amov;g species encom'tered at "orn-^-i-ossive- 

 1; ' i.;;-her horisor.s. l?he Ohipolan ?. flori'^^ar.a Dall '.:„;, :.. c .-al- 



{'^). loc. cit., -0. 1267, pi. 54, fi^-.lO, 1003. 



osahatcViie P. o p i s th o g-r ar. ma t a Dall (5) and the recent P. simnsoni 

 II (4) form, a series exhihitin'^ this featiArc, on the recent shell 



•J c 



f:^). loo. cit., p. 1267, pi. 54, fig. 8, 1903. 



-10 trace of the divaricate sculp tnre oeing noticeable on nnv;orn 

 -~ur"aGes. Dhese species differ from carhasea in outline, as r:ell 



