276 MANUAL OF NATURAL HISTORY. 



IT. ORDER.— Pedipalps (Padipalpi). 



Palpi produced, cheliform or shaped like pincers ; 

 mandibles furnished with a moveable claw, not 

 emitting a poisonous liquid ;. abdomen jointed, with- 

 out spinnerets. 



1. Family. — Scorpions (Scorpionidse). Stigmata 



eight, situated along lower and lateral part 

 of abdomen ; mandibles chelate or ending in 

 two digits, the outer of which is moveable ; 

 comb-like organs on inferior part of thorax. 



2. Family. — Tarentulas (Phrynidae). Stigmata 



four, situated near origin of abdomen ; man- 

 dibles unguiculate or ending in a moveable 

 claw ; thoracic combs none. 



II. SUB-CLASS, — Tracheary-Arachnidans 

 (Trachearia). 



Respiration by means of ramifying tracheal tubes ; 

 eyes two or four, smooth. 



I. ORDER. — Simple-Trachearians (Monomerosomata), 



Body without division, the head, trunk, and ab- 

 domen being united into a single mass ; abdomen 

 not annulated. 



I. SUB-ORDER.— Mites (Errantia). 



Mouth with distinct mandibles ; palpi always pre- 

 sent. Animals free, 



1. Family. — True-Mites (Acaridse). Palpi slightly 

 developed, adherent to the lip; mandibles 



