IDENTIFICATION OF BILLINGS' TYPE. 209 



which is nearly horizontal or slightly sloping outwards and downwards. In the 

 inside of the cup there are ahout seventy thin, sharp, slightly elevated septa, alter- 

 nately larger and smaller. These, in radiating outward across the broad, flat 

 margin to the periphery, are gradually changed into rounded ribs, some of them 

 half a line wide. The body of the fossil, as shown in several weathered and silicified 

 specimens, is composed of numerous irregular infundibuliform layers which are, in 

 some places, in contact, and elsewhere, separated, sometimes three lines apart. Sur- 

 face, unknown. This species shows that Chonophyllum and Pty'chophyllum are closely 

 related genera." Manitoulin island, Clinton formation, Canada West. 



Through the courtesy of Mr. J. F. Whiteaves, of the Canadian survey, 

 we have had an opportunity of examining one of the best preserved type 

 specimens of this species. The above description is of a Ptychophyllum 

 rather than a Chonophyllum, and to this genus we were disposed to refer 

 these forms. However, upon an examination of this type, we find no 

 reason for removing it from the genus to which it was referred by Billings. 

 The turbinate form, the central pit in the calyx, the broadly explanate 

 margins traversed by the widening, convex septal ridges, are all sugges- 

 tive of the genus. These septa do not become angular in the outer area 

 and show no more twisting at the center than may be found in accepted 

 species of Chonophyllum. The specimen is silicified in such way as to 

 conceal the actual structure of the septa, but where it is indicated it seems 

 1 1 > agree; with that already described rather than with that of Ptychophyllum . 

 Until more can be known of the internal structure of these corals they 

 with propriety may be retained in the genus. It is a smaller form than 

 ('. magnificum, with fewer septa. The septal layers are coarser and less 

 strongly bent and the supporting growths are not so well developed, if 

 present at all. Knowing so little of the internal structure of this species 

 and of C. perfoliatum, it is difficult to point out any definite characters by 

 which they may be separated. The septa in the latter are but little 

 twisted at the center, but this character is variable in the same specie-. 



6. Chonophyllum ellipticum, Hall and Whitfield. 



Chonophyllum (Ptychophyllum) ellipticum, Hall and Whitfield. 23d Rep. of 

 N. Y. Stale Cabinet for 1869, 1873, p. 233, pi. ( .», fig. 13. 



"Coral sin ill, subturbinate, laterally compressed, and much distorted in growth ; 

 rays somewhai strongly developed and numerous, very slightly twisted as they- 

 approach the center of the cup. Calyx shallow, with rapidly ascending sides in 

 young specimens, ami spreading nearly horizontally toward the margin in older 

 forms. Exterior of the body covered by a continuous epithecal coating, increasing 

 in strength from In 'low upward. In a vertical section the infundibuliform cups are 

 somewhal distant, broad al the base, with rapidly ascending sides; thespaces be- 

 tween them, air I a Ism between t h- rays, are filled with numerous, irregular, cystos ■ 

 partitions. 



\\\ VI I'.i ii i, im Soi \n V.. i :. 1891 



