CHALK. 75 



now being brought into use. In these coprolites may be 

 constantly seen the teeth and bones of fishes, together with 

 portions of echini and crustaceans, which had passed through 

 the intestines of these saurian reptiles. Fig. 26 is the shell 

 of a small nautilus {Nautilus inequalis) thus found. 



This chalk is of a white colour, very light and porous ; 

 under the higher powers of the microscope, it appears to be 

 made up of organic forms, as " Foraminifera," and portions 

 of various kinds of shells, crushed and broken into minute 

 fragments (fig. 27). Dr. Carpenter, in his work on the 

 microscope, says : " Many parts of it (the chalk) consist 

 in a great measure of the minuter parts of the smaller 



BIG. 28. AMMONITE FROM THE CHALK. 



kinds of Foraminifera, whose shells are imbedded in a 

 mass of apparently amorphous particles, many of which 

 nevertheless present indications of being the worn fragments 

 of similar shells, or of larger calcareous organisms. In 

 the chalk of some localities, Foraminifera constitute the 

 principal part of the minute organisms which can be recog- 

 nised with the microscope ; in other instances the disin- 

 tegrated prisms of Pinna3, or other large shells of the like 

 structure (as Inoceramus), constitute the great bulk." The 



