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Palaeontographica Americana 



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1 1 



13- 



14- 

 IS- 



i6. 

 17. 



PI,ATB XVI 



Figure Page 

 I . A rca Hendersoni Dall 63 



"Oligocene of Bowden ; 2 mm." After Dall. 

 Area Spenceri Dall 64 



"Pliocene of Tehuantepec ; restored left valve ; 18 mm." After Dall. 

 Area Spenceri Dall. "Pliocene of Tehuantepec ; hinge of right valve ; 16 mm." 

 After Dall. 



Area glomerula Dall 64 



"5.75." After Dall. 

 Area glomerida Dall. After Dall. 

 Area polyeyma Dall 64 



"9.75." After Dall. 

 Area polyeyma Dall. After Dall. 

 "Area peefioieii/oides vax. orbieulata Dall ; 8.0." 65 



After Dall. 

 Area peetuneuloides Scacchi 65 



Recent from Finmark ; X 4.4. The posterior ribbing is obscured by the illumi- 

 nation. It is similar to that of the rest of the shell. _ 



Umbonal view of the same ; X 3.8. The ligament occupies only the posterior part 

 of the cardinal area. 



Area pectunei<loidcs ScaccYn ; recent from Finmark ; X4.4. The light streak down 

 the posterior slope was caused by the light used for illumination passing through the 

 thin shell. 

 Area glaeialis Gray 65 



Uddevalla, Sweden ; X 2.63 ; probably Pleistocene. The anterior sculpture is 

 like that on the rest of the shell. To the naked eye this shell appears finely radi- 

 ally striate, but magnification brings out an even reticulation. 



Area glaeialis Gray ; Uddevalla, Sweden ; probably Pleistocene ; X 2.77 ; interior of 

 a left valve. 



Oblique view of the same ; figured to show the cardinal area. 

 Area anomala Verrill and Bush 66 



"Hinge of right valve of type specimen No. 74,081 ; X 10." After \'errill and 

 Bush. 

 Area abyssorum Verrill and Bush 66 



"Interior of left valve of specimen No. 78,793 ; X 6." After Verrill and Bush. 

 18, 19. A rea eidebrensis Smith 66 



After Smith. The indicated dimensions of the figured specimen are: length, 5.5; 

 height, 3.7 mm. 



