THE NAUTILUS. 9 



visit floods had cut the clay banks and turned up a subfossil 

 species of Oreohelix not now found alive on the south rim. 



Thus ends my longest adventure, and perhaps the most 

 fruitful. Collections were made at 187 stations, and with 

 something over 140 sets of duplicates thrown into the basket 

 by generous California friends, we will have about 500 sep- 

 arate lots to check up and discuss later. 



JoUet, III., June, 1918. 



NEW VARIETIES OF NAIADES FROM LAKE ERIE. 



BY N. M. GRIER. 



While the general distinction between the Naiades of Lake 

 Erie and their parent forms of the Ohio drainage have already 

 been commented upon by Walker, ( 1 ) representatives in Lake 

 Erie of at least three of the parental forms have never been 

 given the varietal distinction they deserve. The parent species 

 following the nomenclatorial changes proposed by Friersoii 

 (2) and Vanatta (3) are Fusconaia flava (Raf.), Elliptio dtta- 

 tatus (Raf.), and Symphynota (Lasmigona) costata (Raf.). 

 The comparisons between them and their Lake Erie represen- 

 tatives were made with the aid of Simpson's Descriptive 

 Catalogue. 



ELLIPTIO DILATATUS var. STERKII, new variety. 



Differs from typical dttatatus by its smaller size, less elon- 

 gated and proportionately higher shell. Always inflated, not 

 so pointed posteriorly. Ventral line rather straight, beaks 

 more anterior in position. Epidermis in dilatatiis dark brown 

 and horn or yellowish, surface usually with uneven growth 

 lines. In sterkii, epidermis always smooth or polished, light 

 olive green to yellowish brown to reddish brown. Nacre in 

 dilatatus mostly dark purple, salmon and white ; that of sierkvi 

 ia lavender, light reddish purple, pearl-blue. 



The following table gives maximum, minimum and mean 

 dimensions of 52 shells each of parent and variety : 



