PAL^ONTOLOG V. 1 5 3 



subconical segments, formed by periodical interruptions in i^ the 

 growth of the calyces, resulting in the closure of the marginal parts 

 of the old cells by a continuation of the epithecal wall, and a re- 

 newed growth of a cell, having a narrower basis, from the inner 

 circumference of the old one, until after a wdiile a new contraction 

 occurs. The surface of the stems is delicately cancellated by the 

 intersection of the longitudinal septal rug^e with annular striae of 

 growth. The basal joint of the stems is of conical growth and ex- 

 hibits a strong scar for attachment at the apex. The stems are 

 composed of a cycle of vertical crests projecting from the wall into 

 the cavity, and of a series of superimposed diaphragms intersecting 

 the cavity of the stems and extending from wall to wall, joining it 

 with strongly deflected margins, and only intersected by the vertical 

 crests in the outer circumference. The end cells, which are gen- 

 erally only preserved in small young specimens, are of a dilated fun- 

 nel shape, surrounded by from sixty to seventy alternately large 

 and small lamellae, with granulose surface and denticulated edges. 

 The bottom of the calyces is generally formed by a smooth dia- 

 phragm, but sometimes the crests of the circumference extend over 

 their surface to the centre as low superficial carinas. The lamellse 

 lose their linear crested form on the edges of the calyces, where 

 they expand into low rounded rugse. On one side of the calyx the 

 diaphragms are deeply depressed by a septal fovea, but the latter 

 is not in all parts of the stems equally distinct, and becomes not 

 unfrequently obsolete for a while. The average diameter of the 

 stems is from two to three centimeters ; the length of the joints 

 varies from one to two centimeters. 



Found in the Niagara group of Point Detour and Drummond's 

 Island ; at Masonville, Iowa ; in Perry Co., Tennessee, etc. 



Plate LIV., Upper row. — The outer figure on the right-hand side 

 of the plate is a stem from the original locality, from which the 

 species was first described (Perry Co., Tennessee) ; the three next 

 fragments to the left of it are from the Niagara group of Drum- 

 mond's Island ; the other figures on the left are specimens from 

 Masonville, Iowa. I find it strange that Milne-Edwards should 

 connect this form with the genus Cyathophyllum, which has the 

 most characteristic structure of an Amplexus. 



