THE NAUTILUS. 



89 



Valvatidae. 



Valvata tricarinata (Say). Found on all varieties of bottom, 

 except sandy clay, and in all depths of water down to 18 feet. 

 It occurs in numbers on a sand bottom at four feet, on clay 

 bottom at 3J feet, on a mud bottom at 8 and 18 feet, and on a 

 gravel bottom at 15 feet. It is rare on gravel and boulder 

 bottoms in shallow water. In this area it is usually associated 

 with filamentous alga?, Cladophora or Oedogonium. Many young 

 and immature specimens occurred as well as some variations in 

 the position of the carinae. 



Valvata bicarinata normalis Walker. Occurred sparingly on 

 gravel, sand, clay, and mud bottoms in water 2-6 deep. 



Valvata sincera (Say). This is a deep water form and ocurred 

 on gravel and mud bottoms in water 11 J— 18 feet deep, usually 

 associated with the alga Cladophora fracta. It was most abun- 

 dant in water 15-18 feet deep. 



Physidae. 



Physa warreniana Lea. This tadpole snail occured on all 

 varieties of bottom in water from one half to 11 \ feet deep. It 

 is abundant, however, only in water one half to one and a half 

 feet deep and the the numbers decrease with depth. A gravel 

 or boulder bottom is the normal habitat of this species when 

 adult, but when young or immature, as was the case with the 

 greater number of individuals collected (1-3 mm) it lives in 

 filamentous algae (Oedogonium, Cladophora, Spirogyra). Of 47 

 lots collected in 1916 but six contained adult animals. This 

 seems to be another species that attains maturity in the fall, adults 

 being abundant the previous year, in September, in shallow 

 water where but few immature shells were seen. This form of 

 Physa seems to differ sufficiently from ancillaria to be considered 

 a species and there seems to be no reason why it should not be 

 called Physa warreniana. It varies greatly in the sculpturing 

 of the shell, many individuals occurring that have a smooth, 

 polished shell. 



Physa Integra Haldeman. Occurs on boulder, sand, clay and 

 mud bottoms in water one and a half to ten feet deep. Most 

 abundant on a sand bottom in water one and a half feet deep, 



