438 ARACHNIDA - CHERNETIDEA CHAP, xvi 



running backwards or sideways with their pedipalpi closely 

 folded up against the body. Four genera usually admitted fall 

 within this group : -Obisium, Roncus, Blotlirus, and Chthonius. 



Obisium has four eyes, parallel - sided cephalothorax, and 

 curved chelae on the palps. Roncus is like Obisium except in 

 having only two eyes, and is therefore disallowed by Simon, who 

 also considers Blotlirus to comprise merely eyeless species of 

 Obisium. In Chthonius the cephalothorax is broadest in front, 

 and the digits of the chelae are straight. 



The Obisiinae are found in moss and debris, and under stones. 

 Three species of Obisium. two of Roncus, and four of Chthonius 

 are recorded in England. 



The subjoined list of British species of Chernetidea is taken 

 from the monograph of the Eev. 0. P. Cambridge, cited above : 



GROUP I. Four eyes. 



Chthonius orthodactylus, Leach. 

 rayi, L. Koch. 

 ,, tetrachelatus, Preyssler. 

 ,, tennis, L. Koch. 

 Obisium r ninscoriuit, Leach. 



xiilriitii-inii, C. L. Koch. 

 maritimum, Leach. 



GROUP II. Two eyes. 



Roncus caiiil>rid'j!i, L. Koch. 



lubricus, L. Koch. 

 Chelifer In-.r-mannii, Leach. 



cancroides, Linn. 



nn riilianus, L. Koch. 

 subruber, Simon. 



llr<'i]/ii, 





 



(IROUP III. No eyes. 



Chi'rnes nodosus, Schr. 

 v'/ix//7//x, Camlj. 

 cimicoides, Fain-. 

 dubius, Camb. 

 'jilmliTiiliin, Sinidii. 

 Chiridium muscorum, Leach. 



