Victorian Fossils, Part XXII. 819 



" Owing to tlie soft character of most of tlieir parts, there are 

 comparatively few actual remains 'of Chaetopods in the ohler 

 geological formations, though there are many burrows and tracks 

 wliich have been ascribed to members of that chiss. Tubes of 

 tubicoU)us Polychaeta have, however, been found in formations 

 bating from the Cambrian period onward." Since this was written 

 Cambrian annelids have been described by C. D. Walcott from 

 Jsorth America.^ 'I'hey belong to the Class Chaetognatha (Aniiskwia, 

 Walcottj; the class Chaetopoda, sub-class Polychaeta (order Misloa, 

 Walcottj; and to the class Gephyrea (Fams. Ottoidae and Pikaidae, 

 AValcott). These annelids are preserved in their entire form and 

 pressed flat upon the surface of the shale. They are conspicuous 

 in having a shiny film which lies upon a lighter background of 

 ijhale, and from them Dr. Walcott obtained many remarkable photo- 

 graphs by adjusting the light and carefully re-touching the actual 

 structure seen in the fossil. 



The prostomial gills of Trachyderma here described are also 

 represented by a dark film, on a lighter grey-shale background, 

 but the fossil remains do not exhibit a sheen, as in the Middle 

 Cambrian examples from British Columbia, above mentioned. 



From the Ordovician Shale of Cincinnati, Ohio, Dr. E. 0. Ulrich 

 •described as far back as 1879- some filiform segmented worms, 

 probaly polychaeto in affinities, as Protoscoltx. In the same paper 

 Ulrich figures what is perhaps more interesting from the present 

 ustandpoint, another form, Eotroplionia setigera,^ which undoubtedly 

 represents prostomial appendages of an annelid. 



Those fossils which have been from time to time figured as 

 NereAtes, as for example, N. camhrensi'^^ Murchison,* from theLlan- 

 <leilo of South Wales, I hold to be true impressions of the soft parts 

 -of nereid worms, since the lateral serial lobes are exactly similar 

 in form to the parapodia of certain nereid worms like P/n/IIodoce.-' 

 That they are not due to casual trails of crustaceans, tracks of 

 •molluscs, brown seaweeds or other adventitious agencies seems very 

 •evident from the sharpness of the impressions, although Nathorst'^ 



1 Smithsonian Mi«c. Coll., vol. Ivii, No. 5, 1911. Middle Catnltrian Auiielids. 



2 Jourj). Ciricimiati Soc. Nat. Hi.st., vol. )., 1879, pp. 87 91, pi. iv., fij^s. 1-4. (I am indebted to 

 Dr. Ulrich for a typed copy of this Mcarce work, with photo-rcproduetions of the (ilate). 



.3 Ibid., plate iv , fij^s. .'>, ^a. 



4 Silurian S.\8teni, pt. ii,, 18:^9, p. 700, pi. xxvii. »!},'. 1. Silnria, Srd ed., isr)9, p. 2"20, fossils, 

 p. 221, No. 42{S). Bailey, Char. Brit Koss., 18fi5, i>l. vi., fl^'. «. 



."i Cf. Cainbrid<(e Nat. Hist, vol. ii , 189(5. Polyehaet, WorniH. Benhain, p. ;{14, fig. lOf). 

 6 K. Svenska Vet. Akad. Handl., vol. xviii., No. 7, 1881. Also ibid., vol. xxi.. No. 14, 188(''. 



