i8 4 



HISTORICAL PALEONTOLOGY. 



The Palaocaris typus (fig. 122, <?) and the Anthrapalamon gracilis 

 (fig. 122, /), from the Coal-measures of Illinois, are two of the 

 best understood and most perfectly preserved of the few known 

 representatives of the " Long-tailed " Decapods in the Car- 

 boniferous series. The group of the Crabs or " Short-tailed " 

 Decapods (Brachyura), in which the abdomen is short, not 

 terminated by a tail-fin, and tucked away out of sight beneath 

 the body, is at present not known to be represented at all in 

 the Carboniferous deposits. 



In addition to the water-inhabiting group of the Crustaceans, 

 we find the articulate animals to be represented by members 



Fig. 122. Crustaceans of the Carboniferous Bocks, a, Phillipsia seminifera, of the 

 natural size Mountain Limestone, Europe ; b, One valve of the shell of Estheria 

 tenella, of the natural size and enlarged Coal-measures, Europe ; c, Bivalved shell of 

 Entomoconchus Scouleri, of the natural size Mountain Limestone, Europe ; d, Dithyro- 

 caris Scouleri, reduced in size Mountain Limestone, Ireland ; e, Palceocaris typus, 

 slightly enlarged Coal-measures, North America ; /, Anthrapalcemon gracAlis, of 

 the natural size Coal-measures, North America. (After De Koninck, M'Coy, Eupert 

 Jones, a*d Meek and Worthen.) 



belonging to the air-breathing classes of the Arachnida, Myria- 

 poda, and Insecta. The remains of these, as might have been 

 expected, are not known to occur in the marine limestones of 

 the Carboniferous series, but are exclusively found in beds asso- 



