Distribution of North American Viviparidce. 137 



large. At Bridgeport, in the latter stream are found gigantic 

 specimens which are excelled only, in size, by specimens from 

 the Cumberland at and about Nashville. In the greater tribu- 

 taries of all these streams it occurs but, as in the region north 

 of the Ohio, it does not exist in the smaller streams. West of 

 the Mississippi the species has not yet occurred. 



Over all the western States from Arkansas south to Texas 

 and east to central Alabama ranges a form to which Mr. Lea 

 gave the name of Campeloma coarctation. In the White 

 and Saline and St. Francis rivers in Arkansas as far as Caddo 

 Lake and the Rio Brazos in Texas this shell is very abundant. 

 Eastwards it occurs in numerous streams in Mississippi and 

 south Alabama. The northernmost locality in the latter State 

 is at Helena where it is exceedingly numerous in Buck creek. 

 It appears to be most nearly related to Campeloma subsolidum 

 being related to it somewhat as Campeloma limum is to Cam- 

 peloma rufum. In northern Arkansas it is replaced by the 

 typical western form, Campeloma subsolidum Anthony. 



The genus Lioplax has but two representatives and these 

 occupy not only entirely distinct areas but do not occupy the 

 same drainage systems. The form of widest distribution is 

 Lioplax subcarinata Say. The range of this species is from 

 the Ohio river southwards to and including the Tennessee 

 river ; westwards to Missouri and central Iowa ; northwards 

 the range is limited to Minnesota in which State, at Ft. Snell- 

 ing, in the Minnesota river, it occurs abundantly. In Illinois 

 and Indiana it occurs somewhat numerously in certain of the 

 larger streams. The only Kentucky habitat is the Licking 

 river so far as present information goes. These localities are 

 all west of the Appalachians. East of that system it has been 

 reported only from New Jersey in which State it was originally 

 found. With this exception it is limited to the north central 

 States. 



Its only other congener, Lioplax cyclostomatiformis Lea, is 

 readily distinguished by its greater irregularity of outline, its 

 rounded whorls and its characteristic orange colored aperture. 

 It has occurred only in streams of the Gulf drainage. Under 

 its proper name and the synonymic names of Lioplax spill- 

 manii Lea and Lioplax elliottii Lea it ranges from east Mis- 

 sissippi in the Tombigbee river to Othcalooga creek in Georgia. 

 In the Alabama, Cahaba, Coosa and Flint rivers it is very 

 abundant. Its habit in the Cahaba and Coosa rivers, where we 

 collected it in very large numbers, is very interesting and 

 peculiar. It was found buried in the mud under large, flat 

 rocks, from under a single one of which it was sometimes 

 possible to take 300 or more examples ! It occurred rarely in 



