No. 2.] DAWSON — IMPRESSIONS AND FOOTPRINTS. 67 



impression from Horton Bluff (fig. 2), which at first sight much 

 resembles P. Scoticus, from the Primordial of Roxburghshire, 

 though the Carboniferous specimen is larger and more compli- 

 cated.* It seems to have been produced by the successive 

 pressure of a pair of flat organs, crenated or toothed at the 

 edges, rather than divided into separate toes. Its horizon is the 

 Lower Carboniferous. It was collected by Prof. Hartt. 



The first species of Protichnites referred to above may be ' 

 appropriately named P. Carhonarius, and the second P.Acadicus. 

 They are, I believe, the first impressions of this kind found in 

 the Carboniferous. 



2. Pasiclmifes, Dawson. 



In a paper published in the Canadian Naturalist, 1864, I 

 showed that the sino-ular bilobate markimi:s with transverse 

 striae named Rmophycus by Hall, and found in the Chazy of 

 Canada and the Clinton group of New York, are really casts of 

 burrows connected with footprints consisting of a double series 

 of transverse markings, and that a comparison of them with 

 the trails and burrows of Limulus justified the conclusion that 

 they were produced by Trilobites. I proposed for these and 

 for similar impressions of small size found in the Carboniferous, 

 the name given above. The Carboniferous examples I supposed 

 might have been produced by the species of PhilUpsia found in 

 these beds. A specimen recently obtained from Horton shows 

 this kind of impression passing in places into a kind of Pro- 

 tichnites, as if the creature possessed walking feet as well as the 

 lamellate swimming feet which it ordinarily used. 



I can scarcely doubt that the Cruziana semlpUcata of Salter, 

 and C. similis of Billino:s from the Primordial of Newfoundland, 

 must have been produced by crustaceans not dissimilar from 

 those to which Rusichnites belongs. 



To Rusichnites rather than to Protichnites ought perhaps to 

 be referred certiin transverse linear impressions with a broad 

 central groove from the Lower Carboniferous of Horton, which 

 occur at that place under different modifications, and sometimes 

 seem to change into light scratches or touches of feet employed 

 in swimming, or end abruptly as if the animal had suddenly 

 risen from the bottom. 



* Siluria, 4th edition, p. 153. 



