PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 
EXPLANATION OF PLATE XVII. 
OSTREA INGENS Zitt. .......... 
Patagonian beds ; Shell Gap, lower horizon. 
Inner view of a lower valve of a very large individual, with very much 
elongate area (= phillippii Ortm.), corresponding closely to Zittel’s 
type of O. ingens. 
Natural size. 
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