EXPLANATION OF PLATK IV. 



Pkotkn Madisonilis Say (p. aO). 



FliiS. 1, 2. \'iew8 of jouiiK i JKht :iuil li'ft valves.' 



3. Fragiiii'iit of :i larger valve. 



4. A still hirtjci shell with the anterior ear lost. 



5. A copy of Conrad's lignre of this species, taken from hi.s Mioeeue Foss., PI. XXIV. 



Voi.A HuMPHKEYSi Courad (p. 32). 



Fkj. 6. View of a small lower valve. 

 7. A larger ni)per valve. 

 8, 9. Outer and inner faces of a fragment of a large upper valve. 



152 



