COAL FORMATION. 



The Euomphalus (,fig. 34), (from the Greek, fu, properly, and omphalos 

 the navel,) was a gasteropod mollusk. The shell is 

 often exceedingly thick, and is divided irregularly into 

 a number of compartments or chambers, provided with 

 a solid tube running through them, entirely shutting 

 off that part of the shell in which the animal dwelt, 

 from the smaller and uninhabited portion. These 

 empty spaces served, no doubt, as floats, rendering 1 the 

 whole mass of the shell and animal sufficiently light 

 to move easily in the water. Ansled. 



Fig. 33.Belle'ro. 

 phon costatus. 



Fig. 34. Euom'phalus penta'ngula'tus. 



Fig. 35.Spi'rifer glaler. 



Fig. 36. Productus Martini. 



5. At the period of the Coal Formation, the earth appears tr 

 have been occupied, in a great part, by a deep sea studded with 

 islands, covered by an abundant and luxuriant vegetation. The 

 then existing plants differed very much from those now living ; 

 hundreds of different species are known, but almost the whole of 

 them belonged to the class of vascular cryptoga'mia : they aie 

 principally ferns, equisita'ceae, lycopodia'ceze, that is, plants of a 

 very simple structure but of gigantic size. The tree-ferns, of 

 which existing species do not exceed 20 or 25 feet in height, even 

 in the torrid zone, and generally not more than 8 or 10 feet, then 

 grew, in localities far beyond the tropics, from 40 to 50 feet high ; 

 and other plants, whose representatives of the present time are 

 mere herbs, then rose to 60 feet in height. 



6. In that period, there were also insects resembling weevils and 

 neuro'ptera of the present day ; scorpions, which differed from the 



5. What was the condition of the earth at the period of the coal formation * 



