THE NAUTILUS. 7 



Gap and Hazel Creek. We saw nothing of it on liiglier elevations 

 in the Great Smokies, the localities mentioned lying below 2000 ft. 

 elevation. In the collection of Geo. H. Clapp there is a single shell 

 from the Jas. Lewis coll. labeled " Philadelphia, Monroe Co., Tenn.," 

 probably collected by Miss Law, and measuring: Alt. 13, diam. 24, 

 umbilicus 7t? mm. 



No intergrades with typical P. alternata, P. a. carinata or P. a. 

 costata have been observed. It is remarkable for the strong devel- 

 opment of the secondary sculpture, with line primary sculpture of rib- 

 striae, the unkeeled, capacious whorls, wide umbilicus, and dead, rusty 

 surface. Messrs. Clapp and Ferriss agree with me in considering 

 this a strongly differentiated subspecies. 



The following subspecies of P. alternata are now recognized : 



P. alternata (Say). 



P. alternata fergusoni (Bid.). N. Y. to Md. 



P. alternata rarinotata Pils. Texas. 



P. alternata carinata Pils. Pa. to Tenn., in western division ot 

 the Appalachian Mt. system. 



P. alternata knoxensis Pils. Knox, Blount and Monroe Cos., Tenn. 



P. alternata costata ' Lewis ' Clapp. Greaty Smoky Mts. 



P. alternata mordax (Shut tl.). Great Smoky Mts. (?) 



The last variety has not yet been rediscovered; the " mordax" in 

 collections being referable, so far as I have seen, to a strongly-ribhed 

 form of P. alternata, which has not been named ; and not fulfilling 

 the requirements of Shuttleworth's diagnosis. P. alternata carinata 

 includes strongly angular or keeled, but finely striate shells of the 

 mountainous region from western Pennsylvania to Tennessee. It was 

 defined in my paper on Rhoads' Tennessee shells ; and is not known 

 to occur in the Tenn.-N. C. boundary ranges. I have never seen 

 any true intergrades between /'. alternata and V. cumber landia?ia. 

 and consider the latter a well-defined species. 



Tliere is also a color var. alba Tryon,of P. alternata (Amer. Journ. 

 of Conch, ii. p. 261, and Monog. Terr. Moll. V . S.. p. 40). This 

 occurs abundantly in certain localities within the area of typical 

 alternata. Thus in Philadelphia, alba is found along the Wissahickon 

 Creek, while in other localities in this vicinity the ordinary alternata 

 is found. This color-var. is not really white, but merely albinistic ; 

 it lacks the spots and flames of the typical form. It is also found in 

 Michigan, etc. 



