Spiders and Their Near Relatives 



of the body to members of the Thelyphonidae (p. 18); it was 

 this that suggested the name of the order. They differ 

 greatly from the whip-scorpions, however, both in size and 

 in structure; the larger of the species found, as yet, measure 

 less than one tenth of an inch in length, including the tail-like 

 appendage. 



The form of the body and the more general features of the 



appendages are shown in Fig. 

 13. The thorax appears to 

 consist of only two segments 

 when seen from above, the 

 tergum of the segment bearing the 

 fourth pair of appendages being a 

 part of the carapace. On the 

 ventral aspect of the cephalothorax 

 there are four sternites; a larger one 

 corresponding to the pedipalps and 

 the first pair of legs, and three smaller 

 ones corresponding to the second, third, 

 and fourth pairs of legs respectively. The 

 abdomen is distinctly segmented, and is 

 terminated by a slender appendage con- 

 sisting of about fifteen segments. 



Eyes are wanting. The mouth is a 

 mere slit in an oral prominence, which is 

 situated far forward so that it is partly 

 between the bases of the chelicerse; in other words, the mouth 

 has not migrated so far back as in other arachnids. None of the 

 appendages are furnished with either masticatory ridges or 

 endites. This is the simplest oral apparatus found in the arach- 

 nida. 



The chelicerae are chelate, and are the only chelate append- 

 ages. The pedipalps are leg-like and are terminated by a pair 

 of claws, as are the legs; or to express it differently, the pedipalps 

 have not been modified into organs for some other function than 

 locomotion, as is the case with the more specialized arachnids. 

 It would be correct, therefore, to say that these creatures possess 

 five pairs of legs; but to avoid confusion it is better to restrict 

 the term legs to the last four pairs, as is done in describing other 

 arachnids. Each pedipalp consists of nine segments. 



Fig. 13. K(EN- 

 ENIA WHEE- 

 LERI (after 

 Wheeler) 



14 



