26 



William F. Adams and Susan G. Brady 



WILMINGTON 



Fig. 1. Town Creek and vicinity (* = known range of Helisoma eucosmium, 

 ♦ = known sites of Planorbella magnifica. 



(1945) designation pending definitive studies of soft tissue anatomy. 



Over much of its length, Town Creek is a tidal system approximately 

 30-50 m wide with maximum depths varying between 5-7 m. Whereas 

 the lower reaches are brackish, no salinity has been detected in the 

 area where Helisoma eucosmium occurs. Physical parameters of the 

 water are pH 5.1-7.0 (* = 6.1, n = 3), conductivity 217 //mhos/cm 

 (n = 2), and calcium concentration 107.9 ppm (n = 2). All specimens 

 of H. eucosmium came from a littoral community, occurring in less 

 than 3 m of water, consisting of dense continuous mats of Brazilian 

 elodea (Egeria densa Planchon), fanwort {Cabomba caroliniana Gray), 

 fragrant waterlily (Nymphaea odorata Aiton), spatterdock (Nuphar 

 luteum (Linnaeus)), and floating-heart (Nymphoides aquatica (Walter)). 



