DEVONIAN ROCKS OF CANADA WEST. 125 



spines nearly one line distant from eacli other. Radiating septa, 

 ninety, at a diameter of two inches ; one hundred and eighty, at a 

 diameter of three inches and a half. 



This species is clearly distinguished from S. Sriense, by the 

 greater distance between the arched ridges and spines on the edges 

 of the septa. Judging from some of the fragments, the adult indi- 

 viduals were more than- one foot in length, and three inches and a 

 half in diameter. 



Heliophtllttm Canadense. — (Billings.) 



Simple, turbinate ; surface smooth or annulated, with sharp edged 

 folds ; eighty-five radiating septa at a diameter of one inch and three- 

 fourths. In the bottom of the cup the septa reach the centre and 

 are there twisted together so as to form a somewhat solid elevated 

 pseudo-columella, around which there is a deep space occupied only 

 by the septa. The spines and arched strise are distant about two- 

 thirds of a line from each other. Depth of cup, in a specimen two 

 inches and a half in length, fifteen lines. The adult individuals were 

 probably more than six inches in length. 



This species difiers from IT. Gayugaense in having no smooth space 

 in the botilbm of the cup, and from H. Eriense in the greater distance 

 of the spines and arched strige from each other. 



When the specimens are perfect, the central boss in the bottom of 

 the cup cannot be seen, as the cavity surrounding it is then occupied 

 by the septa, which extend quite to the centre. But when the cup 

 is much weathered, then the septa are usually absent from this cavity, 

 and the central elevation is exposed. There appears to be a septal 

 fossette. 



This also seems to be a large species. One specimen, commencing 

 with a small pointed base, suddenly expands to a diameter of three 

 inches at the length of two inches and a half, and then remains cylin- 

 drical to the cup ; the whole length being six inches. In this specimen 

 there are about ninety principal septa, with an immature series which, 

 when a little more developed, would double the number. Another 

 specimen, eight inches in length, is much curved, and suddenly con- 

 stricted in several places. 



The external characters are so nearly like those of H. Cayugaense, 

 that it will be found extremely difficult to distinguish the one from 

 the other when the cup is not preserved. 



