STANTON : THE MARINE CRETACEOUS INVERTEBRATES. 43 



the number is about four times as great at the periphery as on the 

 umbilical shoulder ; ribs swollen on each side of the venter, which they 

 cross without interruption in the early stages, but on part of the last 

 whorl of the type specimen they broaden and become less conspicuous ; 

 surface also marked by numerous growth lines that curve strongly forward 

 on the middle of the whorls ; suture not visible. 



Diameter, 53 mm.; umbilicus, 10 mm.; height of aperture, 28 mm.; 

 breadth of aperture, 16 mm. 



The species is based on a single small specimen which is evidently 

 related to H.f tardense, but easily separable from it by its more involute 

 form and the differences in the sculpture. 



Locality and position. Ammonite (Belgrano) beds at mouth of canon, 

 four miles east of Lake Pueyrrydon. 



