XII - On the internal structure of some mesozoic brachiopoda

Abstract

The present paper shows how a method of research hitherto but tentatively used by a few workers on the internal characters of Brachiopod shells has been elaborated and applied to certain Mesozoic genera of different families, and has resulted in establishing the relationships of the forms examined more satisfactorily than by methods hitherto employed. It embodies some results of two years’ research on the identification and classification of such numerous species of the Brachiopod families Rhynchonellidae, Terebratulidae, and Terebratellidae, as are found in Jurassic and Cretaceous rocks. At the present time less than half of the Mesozoic Brachiopods are specifically determinable, and little or nothing is known of their internal structure, their mutual relationship, or their evolution. This is probably because internal casts are rare, and in Jurassic and Cretaceous species the two valves are not as a rule found detached from one another.