214 INVERTEBRATA OF MASSACHUSETTS. 



ceding as to give the appearance of a double suture. The surface 

 is exceedingly smooth, no revolving lines being detected by the mag- 

 nifier. The base of the aperture is somewhat narrowed, and pro- 

 longed downwards, and considerably effuse. The twisted fold of the 

 columella is less conspicuous than in P. heterost.ropha. The shell 

 becomes more ponderous and yellowish by age ; and the reddish rib 

 along the outer lip, and the enamel on the columella, much thicker. 



PHYSA ELONGATA. 



Shell thin, slender, elongated, apex acute, pale-yellowish ; whorls 

 six, polished ; suture slightly impressed ; aperture half as long as 

 the shell. 



FIGURE 143. 



State Coll., No. 284. Soc. Cab., No. 1307. 



Physa elongata, SAY; Journ. Jlcad. Nat. Sc. } ii. 171. 



u Shell heterostrophe, pale-yellowish, very fragile, diaphanous, 

 oblong ; whorls six or seven ; spire tapering, acute at tip ; suture 

 slightly impressed ; aperture not dilated, attenuated above, about 

 half as long as the shell ; columella much narrowed near the base, 

 so that the view may be partially extended from the base towards 

 the apex." (SAY.) Length J inch, breadth j inch, diver- 

 gence 34. 



Found in stagnant waters in all the northern and western parts 

 of the United States. In the vicinity of Boston it is rare. 



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

 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 spots 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 respect 

 similar to P. hypnbrum of Europe, unless, perhaps, its spire may be 

 somewhat more produced. 



It is not very common in Massachusetts, and is seldom found as 

 long as the above dimensions ; while Mr. Say gives it y 7 ^ of an inch 

 in Illinois. 



It probably belongs to the genus APLEXUS of Gray (Turtorfs Man., 

 255), which he institutes upon the elongated form of the shell, the 



