FAMILY VALVATID^ 1 23 



.07 ; of aperture i .5 and i .7 mm., in the broadest and narrowest speci- 

 mens, respectively. 



Valvata lewisi Currier. 



Valvata striata Lewis, Proc. Acad. Nat, Sci. Phila., for 1856, p. 260. — BiN- 

 NEY (as var. of sincera), Land and Fw. Sh. N. Am., in, p. 12, fig. 18, 

 1865 ; not of Philippi, 1836. 



Valvata sincera Haldeman {^ro parte), Mon. Limn., viii, pi. i, figs. 6, 7, 8, 



1845. 

 Valvata lewisi Cvkrie.k, List Moll. Mich., Kent Sci. Inst. Misc. Pub., No. i, 

 p. 9, 1868 ; new name for V. striata Lewis, not Philippi. 



Range. — Northern United States from the Atlantic to the Pacific, 

 and northward. 



New England ! Minnesota ! Colorado ! Lake Washington near Seat- 

 tle ! San Bernardino Mountains, Calif. ! Utah ! Lake Superior ! Anticosti 

 Island ! Pine Creek, Manitoba ! Laggan, Alberta, at 

 5,200 feet elevation ; Assiniboia ; Lake La Loche and 

 Peace River, Athabaska ; Great Slave Lake ! Fort 

 Simpson, upper Mackenzie River, N. Lat. 62°! Fig. 94. Val- 

 Frances Lake, head of the Liard River ! Fort Chimo, vata lewisi Cur- 

 Labrador ! Sturgeon Lake, Athabaska ! Upper Colum- rier, |. 

 bia Lake ! (Tyrrell) . 



The name seems to have been originally proposed for a brown muta- 

 tion of V. sincera Haldeman {non Say) , but may well be extended to 

 cover the whole species, which has no other available name. The shell 

 when normally developed and adult has four whorls with a height of 

 3.6 and a diameter of 5.75 mm. It has a much wider umbilicus than 

 var. simplex of tricarinata and is a larger shell, yet usually has a 

 smaller protoconch. The sculpture is axial, fine and close, like the 

 winding of thread on a spool. In the typical form this sculpture is 

 coarser and more prominent than in the less common helicoidea. In 

 both it is largely resident in the periostracum, the decorticated shell 

 being nearly smooth. 



Valvata lewisi var. helicoidea nov. PI. ii, figs, i, 2. 



This form resembles lewisi but is more depressed, almost flat above, 

 and more or less flattened toward the suture ; the whorls are more slen- 

 der and near the aperture usually rather suddenly expanded ; the sur- 

 face is polished, the sculpture frequently obsolete, the umbilicus wide, 

 and its bounding coil peripherally diverted during the grovrth of the last 

 half whorl ; height 2.5 ; of the aperture 2.0 ; diameter of shell 5.0 mm. 



Range. — With the type form, to some extent everywhere, but espe- 

 cially toward the Northwest. Lake Bennett, Yukon Territory ! near 



