1864.] DAWSON ON THE GENUS RUSOPHYCUS. 363 



ON THE FOSSILS OF THE GENUS KUSOPHYCUS. 



By J. W. Dawsox, LL.D., F.R.S., &c. 



The genus Rusopliyciis was established by Prof. Hall for 

 certain transversely wrinkled impressions found in the Clinton 

 group of Oneida County, New York, and supposed to be fossil 

 sea-weeds. Objects of similar appearance have been detected by 

 Mr. Billings in the Chazy sandstone of Grenville, and described by 

 him under the name of R. GrenviUensis. They much resemble 

 one of Prof. Hall's species, R. bilobatus, which is the type of short 

 bilobate forms included in the genus. Similar markings, but of 

 much smaller size, occur in the Lower Carboniferous of Nova 

 Scotia, and have been described and figured by the writer as prob- 

 ably casts of the lower extremities of worm-burrows, in the Journal 

 of the Geological Society of London^ vol. xiv, p. 74. In the 12th 

 volume of the same journal, Mr. Salter had described small bilobate 

 impressions, not striated transversely, from the Longmynd rocks 

 of England, under the name Arenicolites didpna. He supposed 

 them to be burrows of worms. 



Fig. 1. Rusophycus GrenviUensis, var. a, half nat. size. 



I had an opportunity last summer, in company with Mr. J. A. 

 Bothwell, B. A., to examine the locality of th e Grenville specimens, 

 and found them to be quite abundant in certain layers of sand- 

 stone alternating with shale on the bank of the Grenville canal. 

 The facts obtained from their study in place enable me to throw 

 some light on their probable nature, and possibly to rescue them 



