PHYLOGENIC STAGE OF THE GASTROPODA 48 I 



Jour. Geol., Vol. XI, No. 5 Plate II 



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28 29 



Fig. 13, Stenotheca rugosa Hall, after Walcott; \^, Plaiyceras primaevumBiW., 

 restored, after Walcott, X2; 15, Platyceras pri7nordiale Hall, X>^; 16, Subulites 

 exacius SdiT., X^; \T , Helenia bella Walcott; \%, Ecctdyomphalus iriangulus\\h\\.i., 

 X^z; \(), Helicotoma similis Whitf.; 20, SiraparoUina remo/a B\\\.; ^l, Holopea obesa 

 Whitf.,X>^; 22, Trochonema exile, \N'h\ii.; 2^, Pleurotomaria sweeti \S\{\\.i.; ii„ Mur- 

 chisonia putilla Sar.; 25, Raphistoma attleboroughetise S. and F., X4; 26, Raphistotna 

 minnesotense Owen, X^! 27, Raphistoma leiosomellum Sar., XK; 28, Oivenella 

 antiquata Whitf.; 29, Bellerophoti vel Protwarlhia, X%- 



