250 THE CHICAGO ACADEMY OF SCIENCES. 
blunt. The animal is colorless, translucent, so that the in- 
ternal organs (jaw, etc.) may be seen through the body; heart 
beats irregular, ranging from twenty-five to one hundred 
(Sterki says 20 to 110) pulsations per minute. The heart is 
much affected by temperature and activity. For further notes 
see generic description. 
Faw: Wider than high (about four to one); ends slightly 
angular; anterior surface marked by numerous (twenty-five) 
crowded ribs which denticulate the superior and inferior cut- 
ting edges; no median projection; a posterior accessory plate 
is present which extends from the inferior edge (Fig. 77). 
Radula formula: 775+3+4+4+4+3+4+,4!, (13-1-—13); 
central tooth with a base of attachment longer than wide, the 
lower border being somewhat expanded and produced into 
lower lateral projections; reflection short, tricuspid, the central 
MM yw nl WA ThA im 
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b- ; 
Fig. 78. 
Radula of VALLONIA PULCHELLA Miiller. (Original.) c, central 
tooth; 1, first lateral; 6, second transitional tooth; 8, second perfect mar- 
ginal. 
cusp short, wide, the lateral cusps smaller; lateral teeth almost 
as wide as long, bicuspid, the inner cusp long and wide, the 
outer cusp quite small, with only an indication of a cutting 
point, which is well developed in the inner cusp; the base of 
attachment is provided with lower lateral appendages as in the 
central tooth; the fifth and sixth teeth are transition teeth, con- 
necting the laterals with the marginals; these differ from the 
true laterals in having two small, narrow outer cusps (some- 
times unicuspid), and the inner cusp is-shorter; marginal teeth 
wider than long, four to five cuspid, the inner cusp generally 
larger, the outer cusp smaller and comb-like (Fig. 78). There 
are 65 to 70 rows of teeth. 
Genttaha: See generic description. 
Distribution: Europe, Northernand Western. Asia, North- 
ern Africa, Azores, Madeira, North America, and Mauritius, 
Bermuda, New South Wales (introduced?). Not found on 
the Pacific coast of North America. (Sterki.) 
7 : . 
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