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; heat 

 beats irregular, ranging from twenty-five to one hundre 

 (Sterki says 20 to no) pulsations per minute. The heart i 

 much affected by temperature and activity. For further note 

 see generic description. 



Jaw: Wider than high (about four to one) ; ends slightl 

 angular; anterior surface marked by numerous (twenty-fivt 

 crowded ribs which denticulate the superior and inferior cui 

 ting edges; no median projection; a posterior accessory plat 

 is present which extends from the inferior edge (Fig. 77). 



Radula formula: ^+1+4+^+1+1+^ ( I3 _ I _ I3 ; 

 central tooth with a base of attachment longer than wide, th 

 lower border being somewhat expanded and produced int 

 lower lateral projections; reflection short, tricuspid, the centr; 



Fig. 78. 



Radula of VALLONIA PULCHELLA Miiller. (Original.) c, centr 

 tooth; 1, first lateral; 6, second transitional tooth; 8, second perfect ma 

 ginal. 



cusp short, wide, the lateral cusps smaller; lateral teeth almo 

 as wide as long, bicuspid, the inner cusp long and wide, tr 

 outer cusp quite small, with only an indication of a cuttin 

 point, which is well developed in the inner cusp; the base < 

 attachment is provided with lower lateral appendages as in tr. 

 central tooth; the fifth and sixth teeth are transition teeth, coi 

 necting the laterals with the marginals; these differ from tt 

 true laterals in having two small, narrow outer cusps (som 

 times unicuspid), and the inner cusp is shorter; marginal teel 

 wider than long, four to five cuspid, the inner cusp general! 

 larger, the outer cusp smaller and comb-like (Fig. 78). Thei 

 are 65 to 70 rows of teeth. 



Genitalia: See generic description. 



Distribution: Europe, Northern and Western Asia, Nortl 

 ern Africa, Azores, Madeira, North America, and Mauritiu 

 Bermuda, New South Wales (introduced?). Not found c 

 the Pacific coast of North America. (Sterki.) 



