P. E. Raymond — Seaside Notes. 109 



more or less prominently the characteristic cross and the 

 outline of the velum. 



These observations suggest a method by which jelly- 

 fish and other soft-bodied animals may at times have been 

 preserved as fossils. The gelatinous material of the 

 body appears to cement the grains of sand together, and 

 at the same time, the mass of the latter checks the shrink- 

 age. If particles of clay instead of sand covered the ani- 

 mal, the preservation would be much more perfect, and 

 the extreme slowness of decomposition shown by the 

 present specimens would indicate ample time for burial. 



Agassiz 1 long ago made this same observation in regard 

 to the possible preservation of jelly-fish in sand. It is 

 not, however, probable that permanent fossils could be 

 formed in this way under the conditions which prevail on 

 modern sandy beaches. In early Paleozoic times there 

 were, however, extensive flats with aluminous or calca- 

 reous muds which seem to have been inundated periodi- 

 cally, perhaps in periods of persistent onshore winds, and 

 then subjected to long periods of desiccation. These muds 

 became thoroughly dried out and cemented between 

 inundations, and conditions were optimum for preserva- 

 tion in the manner indicated above. 



Trails. 



Among the more common fossils are the little under- 

 stood trails which are so frequently seen on the surfaces 

 of layers of sandstone and shale. It has long been the 

 custom to refer to them as "worm trails," the idea having 

 originated apparently from the fact that the early inves- 

 tigators (see particularly MacLeay in Murchison's Silu- 

 rian System, 1839, p. 699 et seq.) considered them to be 

 the actual impressions of Annelida. Nathorst long ago 

 pointed out that many of them must have been made 

 inorganically, or by Crustacea and Mollusca (K. Svensk. 

 Vetensk. Akad. Handl., vol. 18, p. 66, 1881) and a visit 

 to the seashore should be sufficient to convince any palae- 

 ontologist that he was correct. 



Winding, irregular trails are ascribed to worms, 

 because they look like elongate chaetopods, or masses of 

 their castings. A little reflection, however, will show 

 that it is just these trails, with their sharp turnings, 



1 Contributions to Natural History of IT. S. of America, 1862, vol. 4, p. 63. 



