r^.70 - 



-L'esoription .- "Luoina testa orbiculari, com'oressa, alba, 

 corjcentrice sulDplicata, bifariam oblique striata, inaequilatera; 

 latere anali brevi, rotuncTato; latere bunoali subangiulato, radi- 

 atim 4-siacato; valvula sinistra, Iruaula laevigata, exeavata; 

 intus labro tenuissi'-ae dentiGiilato." f d 'Orbigny, 185S. 



Shell resewbling D. prevarioata but heav' ■-^v -i^nd larger; 

 sculpture coarser; lunule see. Her and deeper; on adult shells tlie 

 cardiiml teeth slightly stronger, but the laterals showing a 

 tendency t^ o p y- . g^-c >> . righ'^ -,■,.-> Q-!:o-::-i or cardinal more obviously 

 and more usually bifid. 



Ji-ensions. - Lat., 14.2 nmi. ; alt., 15.8 ram.; seraidiapi., 

 4.7 mm. 



?.emar>s .- Several valves, which cejanot be rl is t ingui she d 

 from the Miocene and Recent rep:- 'atives, are referred to this 



species. Only one is mature; it is larger than any of the associat- 

 ed prevarioata . The ciifferences betv/een these t- o species are 

 discussed iijider prevarioata . D. chipolana L'all (l), a member of 



il). loG. Git., 1903, p. 1389, pi. 51, fig. 2, 1903. 



Ohipola, Oak Grove and 'Jaloo-c.-c, icuL.. faiuias, reaches a larger size 

 than the fossil forms of guadris::lcata , is typically less inflat- 

 ed, 7;ith more equal and eqxially sloping dorsal nsrgins, occasion- 



