Fresh-Water Shells. 211 



minute, white lines, which are, in truth little parasites [Gordius 

 inquilinus, Miill.) attached like leeches, and which derive their 

 nourishment from the fluids of the animal, without his havino- the 

 power to dislodge them. 



PxiYSA Ancillaria. — (Say.) 



" Shell heterostrophe, sub-globose, pale- 

 yellowish ; whorls rather more than four, very 

 rapidly attenuated; spire trunc: ted, hardly ele- 

 vated beyond the general curve of the surface; 

 suture not impressed; aperture but little shorter than the shell, 

 dilated ; labium a little thickened on the inner sub-margin." 

 (Say.) Length \\ inch, breadth ^-^ inch, divergence OQo, 



Found in Connecticut and Meriimack Riveis, Fresh Pond, &c. 



Animal of a bright lemon-color. 



This shell is distinguished from the preceding by its much shor- 

 ter spire, more angular outline, and especially by its suture, the 

 margin of one whorl being so closely and perfectly applied to the 

 preceding as to give the appearance of a double suture. The 

 surface is exceedingly smooth, no revolving lines being detected 

 by the magnifier. The base of the aperture is som.ewhat narrovv'ed 

 and prolonged downv;ards, and considerably effuse. The twisted 

 fold of the columella is less conspicuous than in P. heterOstroj^ha. 

 The shell becomes more ponderous and yellowish by age ; and 

 the reddish rib along the outer lip, and llie enamel on the colu- 

 mella, much thicker. 



Physa Elokgata. — (Say.) 



"' Shell heterestrophe, pale-yellowish, very fragile, 

 diaphanous, oblong ; whoi'ls six or seven ; spire taper- 

 ing, acute at tip ; suture slightly impressed; aperture 

 not dilated, attenuated above, about half as long as the 

 shell ; columella much narrov.'ed near the base, so that the view 

 may be partially extended from the base towards tlic apex.'' 

 (Say.) Lengtli ^ inch, breadth 4 inch, divergeuee 34o. 



Animal dusky, the head above of an orange hue ; teiitacula 

 rather short and blunt, lighter at tip ; respiratory groove long, 

 narrow and thin, movable in various directions, almost as long as 

 a tentacle, with two black spats like eyes near its tip. 



This species' is easily recognised by its slender, elongated form, 

 and the great proportionate length of the spire. It is in every 



