Fossils of the Chazy Limestone, 



455 



whorls, including a minute one in the apex, five ; height, from 

 one-half to four-fifths the width ; no umbilicus. 



,,V 



Fig. 30, 31, 32. 



Fig. 30. — View of the spire of P. calyx, 

 31. — Side view of same specimen. 

 32. — Side view of a small specimen. 



On the upper surface the first two or three whorls are gently- 

 convex or flat, and constitute a small elevation in the centre of 

 the disc from half a line to two lines higher than the margin. 

 The outer whorls are flat or gently concave, and the last one is 

 in some individuals depressed a little below the margin of the 

 next preceding. Just beneath the margin there is usually (not 

 always) a shallow wide concave band, and below this the whorls 

 are produced downwards with a gentle tapering convex slope, so 

 as to form a conical base which is more or less acute. In some 

 specimens the base is nearly hemispheric, its length being half 

 the width of the spire; but in others it is more conical; and in 

 the one represented by Fig. 31, the length is full four-fifths the 

 whole width. In small specimens consisting of three or four 

 whorls, the outer edge is exceedingly acute, and is bevelled, as it 

 were, by two very narrow flat bands, one above and the other 

 below. In large specimens the edge becomes a little more obtuse 

 towards the aperture, and the small flat bands disappear. 



The upper surface is marked by fine stria? and numerous small 

 furrows or undulations of growth, the whole curving backward at 

 an acute angle with the suture. Tbe markings are interrupted 

 or undulated about the middle of the whorl, so that in crossing 

 the surface from the inner to the outer edge they make two 

 obscurely sigmoid curves. Below the margin the surface is orna- 

 mented with similar stria?, winch, in descending, curve forwards 

 and then backwards. In most of the specimens they are undu- 

 lated below as well as above the margin. 



