12 THE NAUTILUS. 



It is an interesting coincidence that that fecund traveler, Bythinia 

 tentaculata, is the most common shell to be seen on the mud flats of 

 these two marsh areas. — Calvin Goodrich. 



PoLYGTRA MONODON CAVA n. subsp. The shell is larger than 

 P. m. fraterna ; more openly umbilicate, deeply impressed or exca- 

 vated around the umbilicus. Parietal tooth short, its ends about 

 equally remote from the terminations of the lip. Fulcrum well de- 

 veloped, notched above and below. Wliorls 5^. Pilosity fine and 

 short, about as in P. m. fraterna. Alt. 6, diam. 10.5 mm. 



Types No. 90127 A. N. S. P., from Cazenovia, Madison Co., N. 

 Y., collected by Messrs. Henderson, Walker, Clapp and Pilsbry, 

 1905. 



A recent review of specimens in the collection of the Academy of 

 Natural Sciences shows the existence of a rather large and openly 

 umbilicate race in the Transition Zone, from Maine to Minnesota, 

 extending into Ontario. It coincides in part with the range of P. 

 monodon and P. m. fraterna, but does not extend so far south. It 

 intergrades to some extent with fraterna, but in most cases the two 

 are readily separable. 



In this connection it may be noted that with the exceptions of P. 

 m. cincta and P. m. imperforata, the several races of monodon inter- 

 grade more or less. The following races form a series in which each 

 member is connected to the forms immediately following and pre- 

 ceding : monodon, alicia;, friersoni, fraterna, cava, cincta. 



Also in the collection of the Academy of Natural Sciences from 

 the following places : Ottawa, Ontario (F. R. Latchford). Maine, 

 Woodland, Aroostock Co., (O. 0. Nylander) ; Knox Co., (N. W. 

 Lermond) ; Fairfield (J. H. Thomson); Buckfield, Oxford Co., (John 

 A. Allen). Willoughby L. Vermont (A. D. Brown) ; Mass., (Dr. 

 Mighels); N. Y., Herkimer Co., (A. Bailey); Chittenango Falls ; 

 Cazenovia, Madison Co., (H. A. Pilsbry etc.) 



Md., Foot hills of Martin's Mt., Cumberland Co., (H. A. Pilsbry 

 & J. Ives). Va., Harper's Ferry, (G. W. Tryon) Mich., Grand 

 Rapids (A. 0. Currier); E. Saginaw, (Lathrop) Minn., near Albert 

 Lea, (H. Hemphill); Iowa, Des Moines, (T. Van Hyning); Mar- 

 shallton, (Rev. R. B. Kendig). 



The lowest figures on plate 41 of Terr. Air-breathing Moll. U. 

 S. Vol. Ill, seem to have been drawn from a specimen of this 

 variety. — Pilshry\8f Vanatta. 



