1864.] DAWSON ON THE GENUS RUSOPHYCUS. 367 



Taking this view of tlie origin of these singular objects, I 

 would suggest to change the generic name of the Grenville fossil to 

 Rusichnites. In such impressions it is scarcely to be expected 

 that good specific characters can exist. I think it probable, how- 

 ever, that the Grenville specimens may indicate the presence of 

 three species of Trilobites. Some of the smaller specimens are 

 more elongated than the others, and have more numerous furrows. 

 Other and larger ones are shorter and with fewer and more obtuse 

 transverse furrows. A third variety is that referred to by Mr. 

 Billings in his description, as having traces of lateral longitudinal 

 furrows. These may in the meantime be included under R. Gren- 

 villensh, Billings, as varieties (a), (6), and (c). (Figs. 1 and 2). 



My Nova Scotia specimens, though small, show little difference 

 of character, but 1 would regard them as constituting a distinct 

 species, under the name R. carhonarius. (Fig. 3). 



A third species of Rusichnites has recently come into my pos- 

 session, in a collection of fossils from the coal formation of Sydney, 

 Cape Breton, sent to me by my friend llichard Brown, Esq. 

 These impressions are, like the others, casts in relief, on a slab 

 of sandstone. Each impression consists of the casts of contiguous 

 rounded furrows, eacb about one-eighth of an inch in breadth, 

 and crossed by curved undulations and striae, in such a manner 

 as to give the appearance of a pinnate leaf carved in high relief. 

 At each side of these impressions, and about a tenth of an inch 

 distant from them, are interrupted lines, in relief in the casts, 

 and running parallel with the casts of the furrows. The whole 

 has exactly the appearance of the track of the swimming feet and 

 edges of the carapace of a small Liniulus, about half an inch wide. 

 The tracks have also the same tortuous character with those of 

 the modern Limulus. Limuli have not yet occurred in the coal 

 formation of Nova Scotia, though they occur in rocks of this age 

 elsewhere ; but from these tracks I infer that animals of this 

 kind lived in the Sydney coal field, where their remains will 

 probably hereafter be found. I propose for these impressions the 

 name R. Acadicus, and will endeavor to fi<2;ure them in the next 

 number of the Naturalist. 



