On the Pulsations of the Molluscan Heart. 



77 



Conulus fulvus Drap. Pulsations very rapid, and 148 to 150 

 per minute, regular. The heart is situated near the umbilicus. 



Pyramidula alternata Say. The heart is situated 3 mm. 

 from the junction of the peristome with the body whorl, and 

 the pulsations are very regular. Fifteen experiments gave 

 the following record of pulsations : 84, 82 (13 specimens gave 

 these results, the animal being fully extended), 61, 50. The 

 last two were from specimens contracted. 



Pyramidida striatella Anthony. Heart situated as in 

 Vitrea arborea, pulsations regular, and number 87 to 90 

 per minute. 



Polygyra profunda Say. The heart in this species is plainly 

 seen just below the largest brown band, and about 5 mm. from 

 the aperture. An examination of a dozen specimens gave the 

 following data: 70 (3 specimens), 65 (4 specimens), 62 (3 

 specimens), 58 (1 specimen), and 56 (1 specimen). When the 

 animal was held tightly in the hand the record was 56-58 ; 

 when the animal was extended the record was 65-70. 



Polygyra thyroides Say. Heart situated near the upper part 

 of the peristome with the body- whorl ; pulsation irregular 

 (70-73) when contracted, regular (82) when extended. 



Polygyra monodon frater?ia Say. Pulsations regular, 98-100 

 per minute. Heart situated as in leaii. 



Polygyra leaii Ward. Heart situated between the tooth on 

 the parietal wall and the junction of the upper part of the 

 peristome with the body-wall, pulsations varying from 71 to 

 76 per minute (animal extended). 



Polygyra hirsuta Say. Heart situated to the left of the cen- 

 ter of the parietal tooth ; pulsations regular, 60 per minute 

 (extended). 



Polygyra clausa Say. Heart situated on a direct line, mid- 

 way between umbilicus and junction of upper part of peris- 

 ton! with body-whorl; pulsations regular, 88 per minute (ex- 

 tended). 



Polygyra pe?insylvanica Green. Heart situated near junc- 

 tion of peristome with body-wall ; pulsations regular, 85 (ex- 

 tended). 



Succinea obliqua Say. Heart situated midway between an- 

 terior and posterior border of aperture; pulsations regular 

 69 per minute (extended). 



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