iJ39 St. Maurice and Ci^aibornb Pei^ecypoda 229 



PLATE 28 



F igure Page 



1-3. Venericardia pla7iicosta Lamarck 77 



Fig. I, 60 mm., the typical primitive stock from which 

 many American varieties have arisen, likewise the 

 European "type" of the species ; occurring at all hor- 

 ' izons from the Midway to the Jackson inclusive. Spec- 

 imen from the Claiborne "sand". 



2, 62 mm., Claiborne. 



3, the variety we have usually designated by the Greek 

 letter J', (gamma). Large (98 mm. ). From upper 

 Sabine and St. Maurice horizons. Referred by Dall 

 to hornii Gabb. Lisbon, Ala. For interior see next 

 plate. 



4-7. Venericardia rotimda Lea 78 



Fig. 4, 20 mm. , variation with imbricate crenulation styled 

 )^&x^fungina. Claiborne sand. 



5, specimen X 4, showing character of crenulse. 



6, 30 mm., form with few crenulations on narrow ribs, 

 here calXQd funiculus. From the Claiborne sand bed. 



7, 28 mm., same as fig. 6, but showing the usual stage 

 of erosion of Claiborne sand specimens. 



