igog] EvohUion in Palpus of Spiders 63 



alveolus like a ball into a socket. The principal axis is approxi- 

 mately perpendicular to the long axis of the cymbium. Repre- 

 sentatives : 



Thomisidae (in part). 



Agalenidae. 



Pisauridae. 



Oxyopidae. 



Dictynidae. 



3. Fig. 3. This is apparently derived from the second type. 

 The principal axis is not only much shortened, but the bulb is 

 elongated in a new axis at right angles to the principal axis and 

 parallel to the long axis of the cymbium, the alveolus being cor- 

 respondingly extended so as to receive the basal half of the bulb, 

 and therefore oval or elliptical in outline. Representatives: 



Thomisidae (in part) . 



Clubionidae. 



Gnaphosidae. 



4. Figs. 4, 6, and 7. The alveolus is extended so as to 

 include practically the entire ventral face of the cymbium, reduc- 

 ing the latter to a mere concave shell. In the closed palpus the 

 distal portion of the cymbium lies against the side of the bulb, in 

 other words, the principal axis forms an angle much less than 90 

 degrees with the long axis of the cymbium. Representatives: 



Theridiidae. 

 Argiopidae. 

 Mimetidae. 

 Uloboridae. 



5. Fig. 5. The chitinized covering of the bulb, particularly 

 of its distal end, is reduced in extent, so that the bulb is largely 

 composed of thin membrane and is therefore collapsible, in its 

 inactive condition being folded up into a fiat package, almost 

 completely contained in the shallow alveolus, which, as in the 

 first division, is moderate in size. The principal axis is slightly 

 oblique to the long axis of the cymbium. Represented only 

 by the 



Lycosidae. 



These modifications in the form of the bulb and cymbium, 

 which appear so clearly to be designed for the protection of the 

 former, are aided by special modifications or structures directed 



