200 



Annals of the Carnegie Museum. 



" Genus Maclurite. 



" Generic Character. Shell discoidal, much depressed, unilocular \ 

 spire not elevated, flat ; umbilicus very large, with a groove formed 

 by the projection of the preceding whorls, not crenulated. 



"Species M. magna. Shell obtusely carinated on the exterior 

 upper edge ; whorls rapidly increasing in size ; aperture on the left, 

 irregularly oval, horizontally depressed above, lips not reflected." 



Lesueur's original specimens were from Basin Harbor, Vermont, and 

 subsequently other specimens were obtained by him from Kentucky. 

 The specimens actually described as Maclwite magna were undoubtedly 

 from the Chazy formation, as is shown by the figures accompanying 

 the description (Plate 13 of the article cited above). 



Hall's description : 



" Sinistrorsal, discoidal, depressed turbinate; breadth more than 

 twice as great as the height ; spire flat, a slightly depressed line at 

 the sutures; whorls about six, gradually increasing from the apex, 



Fig. 6. A natural section of the operculum of Machirites magnus Lesueur. These 

 sections are very frequently seen on the surfaces of the layers in the middle portion of 

 the formation. 



ventricose, flattened above, obtusely angular on the outer edge ; sur- 

 face marked by fine striae, which, upon close examination, are found 

 to be produced by the imbricating edges of lamellae ; striae undulat- 



