114 LOWER PENINSULA. 



laminar cup-walls, partially connected by the edges of the lamelL-e, 

 otherwise separated by irregular, blister-like cavities, but uniting 

 again in the peripheral wall. Diameter of stems from two to three 

 centimeters. Found in the Niagara group of Drummond's Island, 

 at Point Detour, etc., in silicified, generally much decayed and 

 altered condition. 



Plate XLII. — Surface view and lateral view of specimens from 

 Point Detour. 



CHONOPHYLLUM, Milne-Edwards. 



Single turbinate polyparia, composed of invaginated, radially 

 plicated cell cups, which are intimately united within the central 

 area, and form with their linear plications continuous vertical 

 crests, extending through the whole length of the corallum, and 

 uniting in the centre into a somewhat twisted fascicle, but without 

 composing a solid central axis. The interlamellar interstices of 

 this central fascicle or core are traversed by transverse vesiculose 

 plates, but no larger transverse diaphragmatic septa are observable. 

 In the peripheral area the structure is entirely different. The con- 

 nection between the invaginated cups becomes more loose, the 

 linear plications open themselves and spread horizontally, forming 

 gradually widening and moderately convex, band-like folds of the 

 expanded laminar cup walls, which are superimposed in well-defined, 

 membraniform layers, one reposing on the granulose prominences 

 of the surface of another, and more intimately connecting in the 

 linear furrows between the plications, which correspond to the 

 interlamellar spaces of other Zoantharia rugosa, but were confused 

 by Billings with the lamella;. In his description of Chonophyllum 

 magnificum, Mr. Billings remarks : " The grooves on the floor of the 

 cup indicate the position of the septa, and the ridges are the equiv- 

 alent of the interseptal spaces." This is an evident error. It can 

 be directly observed in the specimens how the linear vertical crests 

 of the central area gradually open in two diverging leaves, spread- 

 ing horizontally into flattened, band-like folds, and at the same 

 time how the spacious interlamellar interstices of the central circle 

 become outwardly angustated in the same measure as the plications 

 widen. In the median line of these linear interstitial spaces, con- 

 founded with the lamclLx, the rows of vesiculose transverse plates, 



