140 R. E. Call — Hypsometric Distribution, etc. 



of 705 feet. Probably this form will be found to range con- 

 siderably higher since we have many examples from streams 

 in northern Georgia whose elevations are near that of Athens 

 or even greater but there is no means of determining the exact 

 height. 



Summing up all the facts gleaned in comparing the eleva- 

 tions of the various localities from which the species of Campe- 

 loma have been sent to us the general statement may be ven- 

 tured that the vertical range is constantly below 1300 feet. 

 Furthermore, at the highest limit of range the species appear 

 to be somewhat depauperate and in other ways show the influ- 

 ence of environmental factors of an unfavorable nature. The 

 several species of Campeloma find expression in greatest num- 

 bers at from 150 feet to 600 feet elevation. Above that limit 

 they are less numerous in individuals. This last range, then, 

 may be safely regarded as the limit of range of optimum 

 stations. 



Of the genus Tulotoma little need be said. Occurring in 

 only one stream, the Coosa river and its continuation the Ala- 

 bama, the range of course is determined by its distribution in 

 that stream. Claiborne, the southernmost limit, is about 16 

 feet elevation ; Wetumpka, the northernmost range, is 185 feet 

 elevation. Within these hypsometric limits, therefore, this 

 genus and its two species are confined. 



The genus Vivipara comes down to within 5 feet of the 

 sea-level in Florida and Louisiana. From this point it ranges 

 vertically to 1150 feet, in a sluggish stream near Eminence, 

 Missouri, tributary to Jack's Fork, in the Ozark mountains, 

 where it abounds. But one species, Vivipara contectoides, is 

 found at this extreme elevation. Thence the range is down to 5 

 feet above sea-level near New Orleans, Louisiana. Like Cam- 

 peloma the genus Vivipara has an optimum hypsometric range 

 which falls between 50 and 500 feet. Of the 4 species which we 

 have recognized Vivipara contectoides has the greatest vertical 

 distribution. The form known as Vivipara subpurpurea comes 

 next with a maximum vertical range of 722 feet, at which ele- 

 vation it occurs in the Minnesota river, at Fort Snelling, Min- 

 nesota. It is practically impossible to make any comparisons 

 between this shell and Vivipara intertexta which also has a 

 similar range ; the latter form, however, does not come so 

 nearly down to sea-level. 



The genus Lioplax has an extreme vertical distribution of 

 about 722 feet which is the altitude of Fort Snelling, Minne- 

 sota, where it occurs abundantly. At the Jefferson Coal 

 Mines, on the "Warrior river, in Jefferson county, Alabama, 

 abundant specimens of the genus, represented by Lioplax 

 cyclostomatiformis, have been taken. The altitude of this 



