Spiders and Their Near Relatives 



three families. The first pair of legs are elongated and are 

 modified into feelers, the tarsus being divided into many seg- 

 ments, the last of which has a rounded tip instead of claws. 

 The ambulatory organs are therefore reduced to three pairs. 

 The respiratory organs are book-lungs; there are two pairs of 

 these; they open on the posterior edge of the second and of the 

 third abdominal segments. 



Among the more important recent general works on this order 

 is that of Kraepelin ('99) which treats of the classification of the 

 order and that of Borner ('04), which is anatomical. 



The order includes three families, each of which is represented 



in the United States; the families can be separated as follows: 



A. Cephalothorax longer than broad with nearly parallel lateral 



margins. 



B. 



l 7- 



BB 



AA. 



Carapace divided by a transverse suture which separates 

 off the part of the thorax bearing the third and fourth 

 pairs of legs; the caudal appendage consists of a single 

 segment, with or without a knob at the end. P 



Shizonotid^e 



Carapace not divided by a transverse 



suture; the caudal appendage long and 



many-jointed. P. 18. Thelyphonid/e 



Cephalothorax broader than long, with 



the lateral margin strongly arched. P. 19. 



Tarantulid/e 



Family SHIZONOTID^E (Shiz-o-not'i-dae) 



Only a few representatives of this family 

 are known; but they are regarded with great 

 interest on account of the generalized condition 

 of the carapace, in which some of the transverse 

 sutures are retained (Fig. 15). The eyes are 

 wanting. Certain light-coloured areas of the 

 cuticula have been mistaken for vestiges of 

 lateral eyes; but Borner ('04) states that there is 

 no modification of the hypodermis below these 

 areas. The caudal appendage is short, either 

 unsegmented or, in certain exotic forms, with a knob-like seg- 

 ment at the end. 



Fi K . is. TRITHY- 

 RFl/S CAMBRTDGEI 

 (after Borner) 



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