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NEW YORK STATE MUSEUM 

 PLATE 6 



Trematonotus alpheus Hall 



(See plate 5, fig. 20-23) 

 Page 54 



Lateral view of a specimen, showing the revolving ribs and 

 the broad transverse folds 



Lateral view of a specimen, showing distinctly the dorsal keel 

 interrupted by the perforations, the alternation of the 

 revolving ribs and the wide and deep umbilicus. From a 

 gutta-percha impression of a natural mold 



A natural cast of the exterior of the apertural part of the last 

 volution and of the interior of the penultimate volution, 

 showing the dorsal perforations of the last volution and the 

 smooth internal surface of the earlier volutions 



An exterior dorsal view of a shell, showing distinctly the inter- 

 ruptions of the revolving ribs by concentric growth and the 

 widening of the ribs upon the lip. From a gutta-percha 

 squeeze of a natural impression 



