What is a name formerly given to certain Silurian brachiopod shells of the genus Spirifer. Delthyris limestone (Geol.), one of the divisions of the Upper Silurian rocks in New York called?

delthyris — A name formerly given to certain Silurian brachiopod shells of the genus Spirifer. Delthyris limestone (Geol.), one of the divisions of the Upper Silurian rocks in New York. (Webster's 1913.)

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