NO. 9 NEW YORK POTSDAM-HOYT FAUNA 26l 



of a gregarious habit, sufficiently heavy to smooth out the ripple 

 marks ; and that it disappeared with the incoming tide. His conclu- 

 sion that it was a moUusk explains some but not all of the facts 

 observed. The impression on the sandstone illustrated by plate 38 

 shows that the front of the body making the impression was curved 

 forward and that the arching lines extended back to the base of the 

 large oval impression made by the under surface of the animal. So 

 far as known to me, there is no recognized mollusk that would make 

 such forward curving lines, and we do not know of any chiton or 

 mollusk capable of making such an impression. In view of this it 

 occurred to me to inquire into the possibility of the trails having been 

 made by an annelid. Since many annelids have been found in the 

 Middle Cambrian Burgess shale fauna ^ there appears to be no reason 

 why remains and trails of large annelids should not be found in later 

 formations. Among the Burgess shale forms there is a large 

 Chastopod worm (Pollingeria grandis^), a crushed specimen of which 

 has a length of 13 cm., width 7 cm. The larger scales found in the 

 same layer of shale indicate that some individuals attained near twice 

 that size. Such an annelid would have had sufficient size, weight, and 

 strength to make the Climactichnites trails. Among recent annelids 

 species of the Aphroditidse attain a large size and some have a shallow 

 water habitat and crawl about on the wet sand between tides. We 

 can readily imagine that such an animal made the tracks under con- 

 sideration. I have not seen any traces of the bristles or stiff setae 

 that occur on the parapodia of most of the Aphroditidse, but this is 

 not unexpected in a sandstone formation. 



A reproduction of the figure of the specimen described by Wood- 

 worth ^ from Clinton County, New York, is made on pi. 40, fig. 2, 

 and on pis. 38 and 39 specimens are illustrated of C youngi from 

 New Lisbon, Wisconsin. Much could be written about the details 

 of these trails, but with the reproductions based on photographs and 

 the descriptions of the figures the student may draw his own 

 conclusions. 



Genotype. — Climactichnites ivilsoni Logan, i860. 



Formation and locality. — Upper Cambrian: (220b) Potsdam sand- 

 stone, Rogier's farm just west of town of Beauharnois, Province of 

 Quebec, Canada. 



^ Smithsonian Misc. Coll., Vol. 57, No. 5, 191 1, pp. 1 10-144, pis. 18-23. 

 "Single scales only are illustrated; Smithsonian Misc. Coll., Vol. 57, No. 5, 

 191 1, pi. 21, figs. 7-9. 

 ^ Bull. New York State Museum, No. 69, 1903, pp. 956-966. 



