Il6 LOWER PENINSULA. 



characterizing them as true interstitial spaces, are, in all the well- 

 preserved specimens, plainly demonstrable, anatomical facts. 



CHONOPHYLLUM MAGNIFICUM, Billings. 



Conical polyparia, attaining a calyx diameter of nine inches in, 

 larger specimens ; some grow in short, broadly expanded polypdoms, 

 increasing but little in length ; others proportionately elongate 

 their stems with the widening of their calyces. The pointed ends 

 of the polyparia are attached by a small scar. The outer wall is 

 annulated by concentric wrinkles of growth and longitudinally 

 ribbed by septal striae. Calyces broad, explanate, dish-shaped. 

 Plications equal, linear, crest-like in the central parts of the calyces, 

 but changing into tent-shape on the spreading neck part, and open- 

 ing into broad bands near their peripheral circumference. The 

 surface of the plications is densely covered with decorative granu- 

 lations or papilli, visible as well on the horizontal, band-like surface 

 as on the side faces of the linear, crest-like portions. In calyces of 

 three inches diameter about ninety plications are counted in the 

 circumference. In the bottom of the calyces the lamellae become 

 very delicately linear and twisted, or irregularly interlacing into a 

 central fascicle. No indication of a septal fovea. Occurs in the 

 upper strata of Mackinac Island and in the drift of the Lower Pen- 

 insula, and is common at the Falls of the Ohio, at Charleston 

 Landing, Indiana, and in other exposures of the upper Helderberg 

 group. 



Plate XLIII., Upper tier. — The right-hand specimen is a silicified 

 fragment of a large calyx exhibiting the band-like form of the 

 lamellae toward the outer margin, and their crested linear form 

 near the central cavity ; the papillose surface is likewise well seen 

 in the figure. The other specimen gives a side view of a specimen 

 showing the general mode of growth, and the laminated structure 

 of the polyparia. The right-hand figure in the lower row is a calyx 

 seen from above. All the specimens represented are from the Falls 

 of the Ohio ; the Michigan specimens were not so well adapted for 

 delineation. 



