General Glasdjicatlon of the Pelecijpoda. 101 



LP = ljiUu-al posterior liunella. 

 IjA=lateral anterior lamella, 

 CA = anterior cardinal. 



rt = anterior portion of an anterior cardinal. 



/»= posterior portion of an anterior cardinal. 



Left valve. Iti<jht valve. 



I.P VI ligt. LA VI 



A. LP IV ligt. LA IV 

 LP II ligt. LA II 



LP VI ligt. CA6 LA VI 



B. LP IV ligt. CA4 LA IV 

 LP II ligt. CA2 LA II 



LP VI ligt. £/; Qa LA VI 



C. LP IV ligt. 46 4^ LA IV 

 LP II list. 2h -la LA II 



LAV ligt. LP V 

 LAJj^ ligt. LP III 

 LAI ligt. LP I 



LA V CA 5 ligt. LP V 

 LA III CA.S ligt. LP III 

 LAI CAT ligt. LPI 



LAV b_a_ 5_^ligt. LP V 

 LA III 3 a 3 h ligt. LP III 

 LAI CAl ligt. LPI 



Diagrams showing the relation of the teeth 

 according to Bernard. 



A. Stage showing primary lamellae only. 



B. Stage showing development of anterior cardinals and laterals. 



C. Stage showing bifurcation of the anterior cardinals. 



Bernard provisionally divided the Heterodonta into two 

 classes. He did not hold these classes to be strictly natural 

 ones, but he made them for the sake of convenience. 



Subdivisions of the Heterodonta. 



A. The Cyrina type, where the CA.I is present, and CA II 



is divided into 2 a and 2 b. 



B. The iyMciwa type, where the first cardinal is undeveloped 



and the second cardinal is consequently simple. 



Families in Bernard's Orders and Suborders. 



Heterodonta. 



Pliodonta. 



MactridfC : 3Iactra, Schizodesma, Lutraria,. Merope, 



Schizotha?rus, Eastonia, Kaeta. 

 Scrobicularidcc: Cumingia, Semele, Scrobicularia. 



