154 LOWER PENINSULA. 



AMPLEXUS YANDELLI, Milne-Edwards. 



Conico-cylindrical flexuose stems, from two to four centimeters 

 in diameter, annulated by fine wrinkles of growth with intermediate 

 coarser rugce, and frequently of a jointed structure through peri- 

 odical constrictions of the calyces and continued growth of the 

 stem without interruption of the continuity of the epithecal wall. 

 Calyces deep, with erect margins, surrounded by about sixty alter- 

 nately large and small vertical crests. The bottom of the calyces is 

 formed by flat or warped diaphragms, depressed on one side by a 

 deep septal fovea. The lamellas are restricted to the outer circum- 

 ference of the diaphragms, but sometimes they extend to the 

 centre as superficial ridges. 



Occurs in the corniferous limestone of Indiana, Kentucky, Canada, 

 and is found in the drift deposits of Michigan. Some cylindrical 

 stems, which evidently belong to the juvenile specimens of Za- 

 phrentis gigantea, are so closely resembling Ampl. Yandelli, that 

 I always find difficulty in distinguishing them. 



Plate LIV., Lower row. — The right-hand specimen is found in 

 the drift of Ann Arbor; the others are from the Falls of the Ohio. 

 The outer specimen on the left-hand side of the plate resembles 

 considerably the basal portion of Zaphrentis gigantea. See Plate 

 LIL, base of large specimen. 



