204 INVERTEBRATA OF MASSACHUSETTS. 



tongue-shaped, nearly as long as the diameter of the shell. The 

 strong angle of the aperture fully displays the respiratory opening, 

 which has a jagged flap, over which lies an acute groove ; move- 

 ments sluggish. 



Inhabits still waters, not so generally pools, as the margins of 

 large ponds. Not very common. 



This species is smaller than either of the preceding, and is at once 

 distinguished from them by the very obvious angularity of the whorls 

 on both sides, and by the very deep, conical cavity of the left side. 

 Sometimes a few faint revolving lines may be found on the surface. 

 The tentacula of the animal are usually very long, but sometimes 

 one or both of them seem to have been broken. 



Planorbis campanula'tus. 



Shell with the last tvhorl distorted, concave on both sides ; lohorls 

 four, strongly carinate on the left, and sub-carinate on the right 

 side ; throat campanulate ; aperture turned to the left. 



Figure 133. 



State Coll., No. 79. Soc. Cab., No. 1265. 



Planorbis campanulitus, Say; Journ. Acad. jWit. Sc, ii. 166. 



Shell discoidal, yellowish or brownish-green, lighter at the 

 sides ; diameter of its tube nearly twice as great from side to side 

 as in the contrary direction ; right side exhibiting scarcely more 

 than two whorls, which are elevated to an obtuse ridge, and form 

 an umbilical vortex very nearly perforating the shell ; on the right 

 side are four volutions, distinctly separated by the suture, which 

 are carinated, and form a shallow, salver-shaped depression ; the 

 whorls enclose each other in a very regular spiral to the last fifth 

 of the outer one, when there is a sudden enlargement and distor- 

 tion towards the left, by which a large, bell-shaped throat is 

 formed ; aperture also dilated, and strongly angular on the left 

 side ; within glazed, reflecting light-blue and brown ; surface 

 regularly marked with fine, transverse, raised lines, and interven- 

 ing grooves. Greatest diameter I inch, at right angles with this 

 I inch, small diameter I inch. 



Found in the larger collections of fresh water, at Fresh Pond, 

 Jamaica Pond, &c. 



