508 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



Not having seen entire specimens of this species, it is with some doubts 

 that it has been referred to the genus Serpula. It seems never to have 

 internal septa as in Vermetus. It was originally placed provisionally in the 

 genus Serpula, and is here, in the same way, retained in that group. 



Locality and position. — Mouth of Vermilion River, Dakota, on the 

 Missouri; in the Fort Benton group of the Upper Missouri Cretaceous 

 series. 



