PAL^ONTOLOG V. 1 1 7 



CHONOPHYLLUM PONDEROSUM, N. Sp. 



Patellate, depressed, conical polyparia of irregular, unsymmetrical, 

 clumsy growth, with gemmation from the centre of the calyces, of 

 single new cells, or, in rare instances, of from two to four confluent 

 or imperfectly defined calyces. End cells shallow, explanate at the 

 margins, more abruptly depressed in the centre, which is surrounded 

 by a cycle of low linear crests uniting in it with twisted ends. 

 Expanded marginal part radiated by fiat, broad, band-like plica- 

 tions of papillose surface. The specimens are all formed of a heavy, 

 compact mass of amorphous, white, ivory-like carbonate of lime, or 

 partially silicified, and with scarcely a trace of the organic structure 

 preserved ; only in a few specimens could enough of it be seen by 

 which to recognize the generic relations of the specimens and their 

 correspondence with Chonophyllum. It does not seem to be the 

 mode of petrification which obscures the structure, as we find this 

 coral in many different localities associated with other corals ex- 

 hibiting the finest details of structure, while they everywhere pre- 

 sent the same massive, compact condition. The coral appears to 

 have, during the progress of its growth, filled out all its cellulose 

 cavities as soon as the fleshy parts of the animal abandoned them. 



It occurs rarely in the upper Helderberg limestones, but is abun- 

 dant in certain layers of the Hamilton group of Thunder Bay, and 

 is also found in Little Traverse Bay. 



Plate XLIIL, Lower tier. — The left-hand figure is a specimen 

 found in the lower limestones of Phelps' quarries, near Alpena. 



OMPHYMA RAFINESQUE, PTYCHOPHYLLUM IN 

 PARTE, Milne-Edwards. 



Single conical polyp cells of Cyathophylloid structure, composed 

 of invaginated calycinal cups, the bottoms of which have the form 

 of spacious diaphragms, either smooth or crested by the radial 

 lamellae uniting in the centre. The ascending side walls of the 

 cups are encircled by linear, crest-like plications, which connect into 

 uninterrupted vertical laminae, within this intermediate area. At 

 the peripheral cup margins the plications become tent-shaped, em- 



