84 INVERTEBRATE ANIMALS. 



I. Order Podosomata. The Sea-spiders are found 

 on Fuci, or under stones near low-water mark on the 

 sea-coast, and are tardy creatures, apparently made up 

 grotesquely of little more than jointed limbs. Pycno- 

 gonum, Nymphon, &c. 



II. Order Acarina. Water-bears, Tardigrada, 

 animalcules found in wet moss, &c. ; Mites, Acari; 

 Water-mites, Hydraclinidce ; the Itch-acarus, Sarcoptes; 

 the harmless parasite on the face, Demodex; and the 

 Ticks, Ixodes. 



III. Order Adelarthrosomata, alr^Xog, concealed; 

 oipSpov, a joint; (ra)|w,a, a body. Harvest-spiders, Phalan- 

 gidce; the Book-scorpion, Chelifer; and the venomous 

 Galeodes of the family Solpugida. 



The biology of this group, of which Walckenaer 

 describes about 450 species, when it shall have been 

 fully investigated, must prove to be deeply interesting, 

 because of the extreme divergency amongst its con- 

 stituents. If the segregation be natural, i.e., if the 

 genealogical affinity be real and close, great indeed must 

 have been the influence of habits and circumstances 

 under which a Galeodes and Demodex, a Hydraclma, 

 a Chelifer, and a Pycnogonum have been evolved from a 

 common and not very remote ancestor. 



Sub-Class ARACHNIDA-PULMONARIA. 

 Respiration by pulmonary sacs, with or without respira- 

 tory tubes ; cephalothorax more or less distinct from the 

 abdomen ; eyes six, eight, or twelve in number. 



Group 195. — Order PEDIPALPI. Scorpions and allies. 

 Head and thorax amalgamated; abdomen distinctly 

 segmented. Estimated number of species, 93 (Walck- 

 enaer). 



