Logan.] The Invertebrates, Benton Group. 479 



tral. The third lateral lobe is small, being less than half as 

 long and scarcely two-thirds as wide as the second lateral, and 

 provided with three nearly equal spreading digitate terminal 

 branches. Between the third lateral lobe and the umbilical 

 margin there are two other small, very unequal, lateral lobes, 

 the first of which has two or three digitations on each side, 

 while the second is nearly simple or but slightly sinuous on the 

 margins." 



This form occurs associated with Scaphites ivarrenii in the 

 Blue Hills shales of the Fort Benton formation. It is found in 

 the outcrops in the vicinity of the White Rock river, in Jewell 

 county, northeast of Mankato. 



Belemnitella bacillus, n. sp. Plate ex, fig. 2. 



Description : Guard cylindrical, expanding gradually toward 

 the pro-ostracum, and coming to a point at the inferior or 

 guard end. Vascular markings moderately well defined ; shell 

 substance thin and marked by parallel lines of growth, curving 

 spirally toward the pro-ostacum. Phragmocone tapering, with 

 a gradually widening superior flange. Length of specimen, 140 

 mm. ; greatest breadth of alveolar cavity, 15 mm. 



Specimen was found imbedded in the Fort Benton limestone, 

 and so crystallized as to make its description and determination 

 difficult. Specimen appears to be closely allied to Belemnitella 

 bulbosa M. & H., but is much larger, and more conical in form 

 than their type. Species is very abundant in the lower strata 

 of the Fort Benton limestone. 



21— iv 



