122 



SUCCINEIDAE 



SUCCINEA OVALIS Say 



Largest of the Succineidae found in Illinois is Succinea oralis. 

 Snails of this species live under leaves and other forest debris 

 that affords concealment during the day. However, in wet 

 weather ovalis snails may often be seen on 

 tree trunks at a considerable height (12-15 

 feet) above the ground, and sometimes even 

 in dry weather they may be found clinging 

 to these high places, the animals having 

 decided to await the next rainy period. Two 

 forms of this species, ovalis ovalis and ovalis 

 optima, are to be found in Illinois. 



Succinea ovalis ovalis Say. Fig. A. The 

 shell of the typical form, first studied by 

 Thomas Say in Philadelphia, Pennsylvania, 

 is small, not exceeding three-fourths inch 

 (18 mm.) in height. It is wide and the spire 

 is short. The width of the shell is about haH 

 the height. 



The shell of ovalis ovalis may be recog- 

 nized by its oval shape, by its very large 

 aperture, which occupies the greater part of 

 the length, and by the peculiar greenish- 

 yellow color of the shell. The decidedly 

 greenish tint upon the rather thin shell is 

 one of the principal distinguishing charac- 

 teristics of ovalis ovalis. 



A rare snail in Illinois, Succinea ovalis 

 ovalis apparently occurs only sporadically 

 in the northern part of the state and is rare in the southern 

 portion. Rock Island, Fulton and Brown counties are repre- 

 sented in Illinois collections. 



Succinea ovalis optima Pilsbry. Fig. B. The large variety 

 ovalis optima, which frequently attains a height of almost 1 

 inch (22 mm.), is distinguished from the typical form by its 

 somewhat longer spire and particularly by its yellow or amber 

 color, which is very dififerent from the greenish shade of ovalis 

 ovalis. The shell is relatively thick, and the surface is marked 

 by coarse sculpture. The long axis of the shell is usually oblique. 

 This variety, the common large Succinea of Illinois, occurs 



