i8o 



OUR COMMON BRITISH FOSSILS. 



bites find their natural history place between the 

 groups above named. Haeckel, however, places them 

 among the " gill-footed crabs " (Branchiopoda\ of 

 which the water-fleas are familiar examples. He does 



r ig. 145. Fossil King-crab, from 

 Coal measures of Coalbrookdale 

 (Belinurus trilobitioides] . 



Fig. 146. Trinucleus fintbria- 

 tus, Upper Llandeilo beds, 

 Builth. 



not tell us on what grounds this is done, for no breath- 

 ing or locomotive organs have as yet certainly been 

 found, although thousands of specimens of all the 

 genera have been carefully examined on their under 



Fig. 147. Compound eye of fossil Trilobite (AsapJius caudatus) slightly magnified. 

 Fig. 148. Ocelli of ditto (magnified). 



sides. Again, the compound eyes of the Trilobites 

 show that they were in this respect really very highly 

 organized, and this highly developed specialization of 

 the sense of sight certainly proves that they ought to 



