TJie Levenshitlme Limestones. 51 



No. 4 group limestone has a very different appearance, 

 both polished and microscopic, and shews the value of the 

 microscope in examining one of these limestones. It does 

 not take a good polish — has dark liver-coloured purple 

 colour with yellow stain-lines and purple blotches — veins of 

 Calcite run across it and the Spirorbis is rare, if at all pre- 

 sent. It has a brecciated appearance, the fragments 

 cemented with calc spar. It appears to have been formed 

 in troubled waters, under disturbed circumstances. A thin 

 section looks like a smear of hematite on the glass slide. 

 Under the microscope it is seen to be made up of minute 

 angular fragments everywhere iron stained. The shells of 

 Entomostraca are here, but no two shells together, and many 

 broken into fragments. 



The 5 th group limestone is again shewn to have an 

 irregular constitution, being made up of curved lines of 

 deposition and crowded with organic remains. Ento- 

 mostraca are in profusion, and a fine " fish eye " centre is 

 there with a red patch in it. The Entomostraca in this 

 section are filled with crystals, probably of calc spar, which 

 form very beautiful objects under the polariscope. The 

 3^in. power reveals curiously jointed tubular organisms, 

 which may be serpulae, or small corals. In many respects 

 this limestone differs from all the others. No more in- 

 teresting object could be found for the polariscope, and it 

 is absolutely crowded with organic remains, which are 

 almost perfect. The Entomostracan which bears the name 

 of Daphnia Primoeva^ here present, so precisely resembles 

 the Daphne of our ponds that Mr. Brothers thought he was 

 looking at that object in the microscope. The coprolite 

 also is extremely interesting under the polariscope, as it 

 shows great diversity of structures and small oval and 

 curved objects, as if the food of the animals which dropped 

 it had been these Entomostraca. 



The 6th group limestones are again extremely in- 



