132 ARACHNIDA. 



Consisting of the families Solpugidce, Cheliferidce, and 

 Phalangiidce, or harvest spiders.* 



ORDER IV. 



Monomer osomat a of Leach, or those trachean species which 

 have the body formed of a single segment, the abdomen pre- 

 senting no tr aces" of articulation, and the moth either suc- 

 torial, or furnished with concealed didactyle chelicera. This 

 order consists of the very extensive Linnaean genus Acarus, 

 or mites, divisible into various families. 



SECTION III. 

 ORDER v. 



Podosomata of Leach, or the Aporobranchia of Latreille. 

 These singular insects are marine ; they are not furnished 

 with distinct spiracles, so that it is probable that respiration 

 is effected by portions of the external covering of the body 

 possessing the properties of branchiae. The body is linear, 

 and^seems, as it were, to be composed only of the union of 

 the legs ; the mouth is tubular and porrected ; and the 

 females are furnished with an additional pair of legs, which 

 serve only for carrying the eggs. This order consists of two 

 faraihes, Pycnogonidce and Nymphonida. 



ORDER I. DIMEROSOMATA. 



This order corresponds with the Linnaean genus Aranea, to 

 which Latreille gave the name of Fileuses or Spinners, Mac- 

 Leay that'^of Araneidce, and Leach that of Dimerosomata. 

 The name of Aranea has not, however, been dropped, but has 

 been employed to denominate the modern genus, consisting 

 of the domestic spider, Aranea domestica of Linnaeus. 



* In order to preserve the order of the mites entire, as suggested by Dr. 

 Leach in theiSupplement to the Encyclopaedia Britannica, I have been 

 compelled to establish a new order for the reception of the remainder of 

 the trachean species, which I have named from the comparatively ob- 

 scure articulation of the abdomen. 



