174 THE CHICAGO ACADEMY OF SCIENCES. 



cool and damp, and affording shade from the sun's rays. The 

 banks of rivers are good localities. 



Remarks: This species is so distinct that it cannot be con- 

 founded with any other. It is rather shy in captivity and 

 quickly retracts within its shell when disturbed. It is not a 

 common species with us, and has thus far been found in but 

 few localities. Those in this area do not seem to congregate 

 together in large numbers, as do many of our snails, but are 

 found either singly or only two or three together. It is a per- 

 fect cannibal, and will very quickly "clean out" a snailery of 

 half a dozen or more common Helices. Thrusting out its long 

 body it crawls into the shells of its victims, and no matter how 

 far the latter may contract within their shells, it is of no avail 

 against the carnivorous appetite of 'Circinaria. It may well be 

 termed the tiger of the Molluscan kingdom. It preys upon its 

 own as well as upon other species, thus being in truth a canni- 

 bal. Thus far it has only been found in the northern and 

 western regions. Concava has been found at Bowmanville 

 under "starting" bark at a height of four feet from the ground. 

 The animal is very nervous in progression, constantly extend- 

 ing and retracting its eye-peduncles, the shell swaying from 

 side to side with a wabbly motion. 



On May 18, 1897, two individuals were seen in copulation; 

 the coitus lasting over ten hours (from 8 o'clock a. m. until 6 

 o'clock p. m.); the eye-peduncles were almost drawn into the 

 head, and the foot was contracted to form a long oval; the 

 heart beat very slowly, nineteen pulsations being counted per 

 minute (about eighty being normal) and the beats were very 

 long. 



Superfamily Aulacopoda. 



"Animal with well-developed pedal grooves. Shell sharp- 

 lipped." (Pilsbry.) 



FAMILY ZONITID.E. 



"Marginal teeth with narrow, elongated basal-plates, and 

 either unicuspid and thorn-shaped by suppression of side cusps, 

 or bicuspid by elevation of outer on middle cusp. Tail gland 

 often present, and sole frequently tripartite."* 



*Pilsbry, Guide to Helices, p. XXVIII. 



