KEY TO CLASSES AND ORDERS OF ANIMALS 25 



8(9) Thoracic appendages all biramous. (Pratt, 382; 

 W. and W., 844.) Order Schizopoda 



9(8) Thoracic appendages not all biramous. 10 



10(11) Eyes stalked; abdomen large, wider than the narrow 

 cephalothorax. The first five pairs of thoracic append- 

 ages are used for seizing and holding food. The second 

 pair is largest. The last three pairs of thoracic append- 

 ages are small, biramous appendages; marine. (Pratt, 

 3^2>-) Order Stomatopoda 



11(10) Eyes sessile; abdomen narrow; carapace small leaving 

 last five thoracic segments uncovered; marine. (Pratt, 

 384) Order Cumacea 



12(7) Carapace covers entire thorax, usually well developed 

 and more or less calcified. The posterior five pairs of 

 thoracic appendages are uniramous, although they may 

 in part be provided with pinchers. Marine, fresh 

 water, and terrestrial. (Pratt, 384; W. and W., 844.) 



Order Decapoda 



Class ARACHNIDA 



1(2) Marine arachnids of large size bearing gill books on 

 the abdomen; with a long, spikelike tail. (Pratt, 

 400.) Subclass Xiphosura 



2(1) Mostly terrestrial arachnids, if aquatic, small and 

 without a long spikelike tail. 



Subclass Arachnida, p. 25 



Subclass ARACHNIDA 



The following key to the orders of the Arachnida is taken with 

 some slight modification from Comstock's Spider Book. 



1(14) Adbomen distinctly segmented 2 



2(13) Animals not wormlike parasites. 3 



