286 Mr. Brockbank and Mr. C. E. de Range on 



called — are conchoidal, and frequently the broken surfaces 

 have a waved appearance, like rounded creases. The grain 

 is beautifully regular, and it takes a high polish. It is in 

 fact a marble of a beautiful pinkish grey colour. It is mottled 

 all over with greenish circular spots, some with dark centres. 

 These spots pervade every bed, but there are fewer in the 

 upper, whilst the lower marbles are so thickly mottled as to 

 be almost made up of mottlings. These green spots 

 appear to be indications of the presence of organic remains.. 

 Some are certainly coprolitic, and others are produced by 

 Entotnostraca^ Annelida, or other minute organisms, whose 

 shells make up the mass of the limestone. One of the 

 thicker beds of this first group contains large numbers of 

 grey nodules, which are clearly coprolitic, and which, under 

 the microscope, are seen to contain reddish specks, hematite- 

 stained, as in the case of the fish remains which abound in 

 the same rocks. In one remarkable instance a small tooth 

 is to be seen in the coprolite. The small annelid Spirorbis 

 Carbonarius — formerly known as Microconchiis Carbonaria — 

 is present in all these limestones, but more sparingly in the 

 upper beds. It becomes more and more abundant in the 

 lower beds, until in some instances the rock appears to be 

 absolutely made up of its remains. 



This first group of limestones has a very different 

 appearance in every way, except colour, from those that 

 follow. It was evidently formed in very quiet waters,, 

 where small fishes fed on the tiny annelids and crustaceans,, 

 and where the currents were gentle and recurrent. The 

 beds are perfectly regular, and the limestones contain the 

 remains of the small fish, always in fragments — single scales,, 

 and odd detached spines ; as if they had been entombed in 

 this fragmentary state. The green shales which coat the 

 limestone are similar, and contain the same fragmentary 

 remains of fish — hematite-stained, and always beautifully 

 preserved. Leaia Leidyivd.x. Williamsonia was found in these 



