THE SPIDERS OF EPPING FOREST. 183 



V. A Systematic List of the Spiders of Epping Forest, 

 including brief descriptions of families, 

 genera and species. 



I.— ANATOMY.' 



Body. The body or trunk consists of two well-defined parts, 

 Cep halo -thorax and Abdomen, connected by a slender 

 Pedicle or waist. 



Cephalo-thorax. This is the anterior great division of the 

 body, consisting of the Caput or head, and the Thorax. 

 These two parts are fused together, a more or less 

 distinct linear impression usually indicating the junction. 

 Traces of original segmentation of the thorax are as a rule 

 apparent in the form of depressed lines termed lateral 

 impressions which converge upon a more or less distinct 

 central impression (occasionally absent). The integument 

 of the cephalo-thorax is of a more or less firm and 

 resistant character ; but in the case of some species in 

 which the abdomen is protuberant anteriorly, the 

 posterior portion of the thoracic integument becomes of 

 a somewhat pliant nature. The caput is more or less 

 wedge-shaped posteriorly. Upon the posterior portion 

 of the upper surface of the thorax is occasionally found 

 a stridulating organ The length of the cephalo-thorax 

 should be taken as implying the direct distance between 

 the lower edge of the clypeus and the central part of 

 the posterior margin of the thorax. This measurement 

 is best made by means of an accurate divider with 

 curved needle points. 



Connected with the cephalo-thorax are the follow- 

 ing structures, which are described separately : — Eyes, 

 Sternal-plates, Falces, Palpi, Legs. 



Eyes. The eyes of spiders are invariably simple and are 

 normally eight in number. In a few British species 

 only six are present, whilst in some exotic spiders the 

 number is still further reduced to four or occasionally 

 two. , Two forms of eyes are found, which Mons. E. 

 Simon, conceiving a difference in their respective 

 functions, designates diurnal £yes and nocturnal eyes. 



2 See Plates VII, and VIII., with the explanations thereof on pp. 189-90 post. 



