Handbook of Paleontology 47 



former ; fine lamination or lack of bedding the latter. 

 The texture of the materials indicates the strength of 

 currents and the direction is shown by inclusions, such 

 as fossils and pebbles, and by such structures as cross- 

 bedding, ripple marks, rill marks, wave marks etc. In 

 lake and marine deposits coarse sediments indicate 

 shallow water deposits ; finer sediments deep water de- 

 posits. The character of the fossils also helps out 

 here. Marine limestone deposits very often are deep- 

 water deposits, but more than this they indicate clear 

 water conditions. Continental deposits may be dis- 

 tinguished from marine and littoral deposits. When 

 fossils are present they are distinction enough. Aside 

 from this, marine deposits show less variation in char- 

 acter, have comparatively uniform bedding and may be 

 of enormous thickness. In more shallow water they 

 may show ripple marks, but mud cracks, rain prints 

 etc., so characteristic of tidal areas and flood plains of 

 rivers, are not to be found. Littoral deposits are never 

 of great thickness. Their fossils, when present, are 

 characteristic. They have, in common with conti- 

 nental deposits, ripple marks, rill marks, rain prints, 

 suncracks, tracks and trails etc., but these structures 

 are more apt to be found in muds of continental origin. 

 Littoral deposits consist chiefly of sandstones with 

 associated conglomerates and mudstones. Continental 

 deposits may contain fresh-water, brackish water or 

 land fossils, never marine. Some of these deposits at- 

 tain great thickness. Wind and glacial deposits are 

 very characteristic, and also delta deposits, which 

 when laid down in the sea show a mixture of conti- 

 nental, littoral and marine deposits. The finer conti- 

 nental deposits may show sun cracks, rain prints, foot 



