270 \V. II. SIIERZER — THE GENUS CHONOPHYLLUM. 



"The distinctive features of this species consist in its elliptical outline and dis- 

 tinctively marked rays. There may be some doubt as to its generic relations- 

 The rays are very slightly twisted as they approach the center of the cup, hut 

 there is no appearance of a columella. The great development of the rays, and 

 the continuous epithecal coating, arc features which pertain more particularly to 

 Ptychophyllum than to Chonophyllum. 



"For, until), i ami locality : In the marly beds at Rockford, Iowa.'' 



An examination of s] >ecimens from the same localhVy (Hamilton group) 

 shows lamellar septa, well-developed horizontal tabula? through nearly 

 one-half the visceral cavity, and in the outer area a very coarse vesicular 

 structure. After describing his Cyathophyllum houghtoni from the Hamil- 

 ton group of Michigan, Dr. Rominger adds:* 



"A coral described by Hall under the name of Chonophyllum ellipticum, from the 

 Hamilton group of Iowa, agrees in structure with the described form, but not with 

 < Tionophyllum." 



The specimen figured on plate xxxvi, upper tier, center, shows a struct- 

 ure very similar to that seen in vertical sections of Chonophyllum ellipticum. 



7. Chonophyllum ponderosum, Rominger. 



Chonophyllum ponderosum, Rominger. Geol. Sur. of Midi., vol. iii, pt. ii, 



1870. p. 117, pi. xliii. 



This peculiar coral, in regard to the generic relations of which there is 

 no doubt, is from the lower Devonian strata of Michigan. It was thus 

 originally described : 



" Patellate, depressed, conical polyparia of irregular, unsymmetrical, clumsy 

 growth, with gemmation from the center 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 center, 

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

 Expanded marginal part radiated by flat, broad, band-like plications 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 corre- 

 spondence with Chonophyllum. 



" It does not seem to be the mode of petrifaction which obscures the structure, as 

 we rind this coral in many different localities associated with other corals exhibit- 

 ing the finest details of structure, while they everywhere present the same massive, 

 compact condition. The coral appears to have, during the progress of its growth, 

 tilled out all its cellulose cavities as soon as the fleshy parts of the animal aban- 

 doned them. 



" It occurs rarely in the Upper Helderberg limestone, but is abundant in certain 

 layers of the Hamilton group of Thunder hay, and is also found in Little Traverse 

 bay." 



i ■■ ol. Sur. of Mich., vol. iii. pt. ii, p 105 



