Spiders and Their Near Relatives 



A single species belonging to this family has been found in 

 the United States; this is Tritbyreus pentapeltis (Tri-thyr'e-us 

 pen-ta-pel'tis), which occurs in the desert regions of southern 



California. Only a few specimens have 



Q^-~--x been taken; the largest of these meas- 

 f \ ured less than one half inch in length. 



Figure 16 represents some of the details 

 of structure of this species as given by 

 Cook ('99). 



Family THELYPHONIDAEfThel- 

 y-phon'i-dae) 



This family includes the tailed 

 whip-scorpions, those in which the 

 caudal end of the abdomen is furnished 

 with a slender, many-jointed appendage 

 (Fig. 14). In this family the carapace 

 is not divided by transverse sutures. 

 Eight eyes are present, two, the 

 median eyes, near the centre of the front 

 part of the head, and a group of three, 

 the lateral eyes, on each side farther back. The pedipalps are 

 stout and armed with tooth-like proc- 

 esses (Fig. 17). They are semichelate, 

 the projecting process of the fifth seg- 

 ment being much smaller than the sixth 

 segment which forms the other part of 

 the chela; in the ordinary chelate type 

 the opposite of this is the case. These 

 pedipalps are remarkably developed for 

 crushing the prey; they might be de- 

 scribed as plurichelate; for in addition 

 to the pincers formed by the fifth and 

 sixth segments, another pair is formed 

 by the fourth and fifth; and the second 



segment bears a prominent semicircular process, armed with 

 strong teeth, which can be opposed to the third and fourth 

 segments. The chief use of this process of the second seg- 

 ment is to be opposed to the corresponding process of the other 



18 



Fig. 16. TRITHYREUS PEN- 

 TAPELTIS (after Cook), o, body 

 without appendages; b, carapace 

 more enlarged; c, caudal segments 

 lateral view 



Fig. 17. THE PALPUS OF 

 MASTIGOPROCTUS 



