68 



GEOLOGY. 



the West Indies ; whilst Trigonia only occurs in the seas of 

 Australia. 



Class V. Brachiopoda ("Lamp-shells," ex. Terebratula). — The 

 British collection of Brachiopods or " Lamp-shells " occupy Table- 

 cases 86, 87, and 88. The Tertiary, Cretaceous, Oolitic, Carbon- 

 iferous, and Devonian forms being well represented, also those of the 

 Upper Silurian strata. 



The foreign species occupy Wall-cases 10 and 11. The Brachio- 

 poda have received special attention from Mr. Thomas Davidson, 

 LL.D., F.R.S., who has devoted his whole life to the study, illus- 

 tration, and description of this class of the Mollusca. Many of the 

 specimens figured by him may be seen in the collection. 



Class VI. Poltzoa (Sea-mats and horny Corallines). — These 

 elegant organisms, so frequently found upon the sea-shore, and often 

 confounded with sea-weeds (Algse), are really the horny or calcareous 

 composite habitations of numerous distinct but similar microscopic 

 zooids, each individual occupying a minute double-walled sac, in a 

 common habitation, called a coenoecium, or polyzoarium. 



They are met with in great variety of form in the Coralline Crag of 

 Suffolk, in the Miocene of Dax, Bordeaux, and Touraine, and in the 

 Eocene Beds of the London and Paris Basin. 



Beautiful masses of Fenestella are found in the Permiau or Mag- 

 nesian Limestone of Durham, and in the Permo-Carboniferous rocks 

 of Australia and Tasmania. The Polyzoa of the Carboniferous for- 

 mation are also numerous and varied. The most singular of these is 

 the ArcJiimedipora , which has its ccencecium, or polyzoarium, arranged 

 around a central screw-like axis, giving it a most elegant geometrical 

 form. 



Division B. Arthropod a (Jointed Animals). 



Class 1. Insecta (ex. Beetles, Flies, Bees, &c). 

 ,, 2. Mtrtapoda (ex. Centipedes, Millipedes). 

 ,, 3. Arachnida (ex. Spiders, Scorpions, &c). 



Insects, Myriapods, and Arachnida are very rare in the rock-forma- 

 tions of this country. They have, however, been met with in con- 

 siderable numbers in the Eocene strata of Gurnet Bay, Isle of Wight, 

 in the Purbeck Beds of Swanage, Dorset, in the Great Oolite of 

 Stonesfield, the Lias of Warwickshire, the Coal-measures of Coal- 

 brook-dale, and Scotland, &c. (see Table-case 84). They are more 

 abundant in the Brown Coal of Bonn ; in the Amber from the 

 Miocene Beds of Samland on the Baltic ; from (Eningen, near 

 Constance ; and from the Lithographic Stone of Solenhofen, 

 Bavaria. From the last-named locality beautiful Dragon-flies 

 (Libellulm) and numerous other genera have been obtained (see 

 Wall-case No. 1 2). 



Class 4. Crustacea (ex. Crabs and Lobsters). — The Foreign 

 Crustacea occupy Wall-cases 12, 13, and 14, and the British forms 

 fill four-and-a-half of the adjoining Table-cases — 80-83. Those 



