THE NAUTILUS. 57 



before me there is an impressed longitudinal line which interrupts 

 12 of the varices. When older the animal corrected this irregularity. 

 This line will probably be found absent in other individuals. 



It seems remarkable that so striking a shell as this form has here- 

 tofore escaped notice. The habitat of the type, which is in the 

 writer's collection, is supposedly China. 



NOTE ON THE DISTRIBUTION OF MARGARITANA MONODONTA SAY- 



BY BRYANT WALKER. 



In commenting, recently, on the distribution of this species (Proc. 

 Mai. Soc., IX, pp. 137-139, 1910), I stated that although it had not 

 been cited from the Ohio east of Cincinnati nor from the tributaries 

 of the Tennessee above Knoxville, in the absence of any records of 

 its occurrence west of the Mississippi, south of Iowa, nor in that 

 river below Adams County, Ills., "the inference would be that its 

 original point of dispersal was in the east, and that it had migrated 

 westward by two routes, one down the Ohio and thence into the 

 Mississippi Valley, and the other down the Tennessee from its tribu- 

 taries or head-waters. That it reached its present range by a migra- 

 tion from the southwest is, in view of the known facts of its present 

 distribution, quite improbable." 



Since the above was written some additional data of considerable 

 interest have been received. 



In the fall of 1910, acting under the instructions of the U. S. Fish 

 Commission, Mr. A. H. Boepple explored the Cumberland River 

 from Pineville, Ky., to Celina, Tenn. In his progress down the 

 river he found M. monodonta at the Sloan Shoals near Burnside, 

 between Eads' Landing and Rowena, and at Cloyd's Landing. 



I have also recently received the species from three localities in 

 the Clinch River, Tenn., viz., near Needham's Ford and between 

 Kelly and Sharp's Ford, Union County, and between Agee and 

 Offut, Anderson County. 



These records definitely determine the occurrence of the species 

 in all of the principal rivers that unite to form the Tennessee, ex- 

 cepting the Powell and the French Broad, and its presence in the 

 Clinch makes it reasonably certain that it will also be found in the 

 former. The head-waters of the latter rise in another, quite differ- 



