40 E-UPERT JoNESj on Bivalvc'd Entomostraca. 



Whether we crumble clown a friable freestone, such as the 

 Bath stone or many of the Oolites of the INlidland Counties — 

 whether Ave powder a piece of Chalk, or reduce a piece of 

 Lias or other clay in water, we shall find abundant well-pre- 

 served relics of ancient Microzoa in the dried and sifted dust. 

 If we take a j^iece of limestone, whether from Dudley, Mat- 

 lock, or Westmoreland, or go abroad for our specimens to any 

 part of the world, we shall find in polished slices of the lime- 

 stone more or less distinct evidences of perfect little shells of 

 peculiar forms, requiring a strong microscope for their eluci- 

 dation. 



Among these microscopic fossils are some that play a more 

 important part than others in the making ujj of the stony 

 masses of many parts of our own country and of other lands. 

 There are in particular two kinds of very frequent occurrence 

 in clays, freestones, limerocks, marbles, chalk, &c., namely, 

 minute Crustacean animals, and another set of Microzoa called 

 Foraminifera. Of each of these kinds there are innumerable 

 individuals living at the present day. These tiny creatures 

 are as easily to be found in the living state as in the fossil 

 condition ; they have had great books written about them ; 

 and they not only afford much instruction to naturalists who 

 study their structures and observe their habits, but they can 

 be a source of much interest to any one Avho has an aquarium 

 — the now frequent ornament of our parlours. 



On this occasion I have to explain the nature of the micro- 

 scopic Bivalved Crustaceans, to allude to their ways of life, 

 and to draw attention to some of the facts connected Avith 

 their being found fossilised in clays and stones. 



The common Crab and Lobster are important members of 

 the Crustacean group of Animals ; so also are Shrimj^s, 

 Prawns, Sandhoppers, Woodlice, the King-crab of the 

 Moluccas, and many others, which are only noticed by the 

 naturalist and seen in museums. 



A characteristic feature of the Crustaceans is their jointed 

 structure (placing them among the Articulata or Arthropoda^, 

 and their Ijeing for the most part coated with a hard, tough 

 armour — the part that covers the front of the body being 

 usually formed of a large plate or buckler (called the Cara- 

 pace or Cephalo thorax j, and the rest consisting of ring-like 

 segments. 



The Shell (or Test) of the Lobster well illustrates this. 

 In the Crab, however, the body is more shrunk up, as it 

 were, beneath the Carapace, which is widened and enlarged, 

 Avhilst the jointed tail-piece is very small and folded neatly 

 underneath. The organs in the Crab are, as it is said. 



