MOLLUSCS, VERMES AND HYDROZOA 



FIG. i6i. Succivea obltqua. 



I 



S. obltqua. Fig. i6i, has a % to 1 54; inch long, ovate, thin and fragile 

 pale-green or amber shell, which is faintly striated and roseate in color at 



the apex. It has three whorls 

 of which the body whorl is 

 large and much expanded, 

 and about % the length of the 

 shell. The spire is very small, 

 the aperture oval and is two- 

 thirds the length of the shell. 

 The body has a yellowish- 

 brown color which shows through the semi-transparent shell. This snail 

 is quite generally distributed in New York, Pennsylvania, New Jersey and 

 Georgia. It is destructive to aquarium plants. 



S. retusa. Fig. 162, has a J/^ to % inch long somewhat conical ovate- 

 oblong very thin pellucid yellowish-white minutely striated shell of three 

 whorls, of which the body whorl 

 constitutes nine-tenths of the 

 entire shell and tapers gradually 

 to the apex. The spire is short, 

 the suture indistinct, and the 

 aperture four-fifths the length 

 of the shell. The body is a 

 little longer than the shell, of a translucent greyish color marked with 

 black spots. This snail is found quite generally in the Eastern and 

 Middle States. 



Lymn^a. This numerously represented genus is found in stagnant 

 and sluggish water, ponds and streams; feeding upon waste matter and 

 aquatic plants, as all the genus are herbivorous and a few species also 

 carnivorous. They are active, prolific and thrive in the aquarium, but are 

 destructive and constant feeders, preferring the healthy growing plants to 

 algse and decaying vegetation; though they are also effective scavengers 

 and devour animal substances and food offal, and sometimes their own 

 spawn. When bred in the aquarium they considerably loose their destructive 

 habits and become feeders on algte. All are air breathers and will leave 

 the water to rest upon aquatic plants, but only at long intervals. The 

 shells of this family are all dextral. 



L. stagnalis. Fig. 163, is the largest representative of this group, the 

 shell reaching a length of i ^ to 2 inches. Itisusually of a greenish-white or 

 yellowish-grey color; of six or eight whorls; of which the body whorl is 

 larger, fuller and rounder than the others, which are drawn to a long, 

 graceful dextral spiral, terminating in a finely pointed apex. The suture is 



FIG, 162. Succhea r etusa. Enlarged. 



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