14 Annals Entomological Society of America [Vol.11, 



chief axis of the animal (Fig. I. pro). It corresponds therefore 

 to the "inner" surface of the front legs, or to the "outer" surface 

 of the hind legs in spiders. It also corresponds to the "inner" 

 surface of the chelae in Theraphosidae called "anterior" in true 

 spiders. 



4. The Retrosymmetrical Surface (should be retropara- 

 symmetrical) is the lateral surface nearest to the posterior end 

 of the chief axis of the animal. It corresponds to the "outer" 

 side of the front legs or to the "inner" side of the hindlegs. 

 (Fig. I. retro). In the chelae it corresponds to the "outer" 

 surface Theraphosidae, or "posterior" in true spiders. 



The four edges or lines of intersection of the four surfaces 

 mentioned in those cases when the appendages are not cylindri- 

 cal in form may be called "epipro" (Fig. 2. ep), "epiretro" (Fig. 

 2, er), "hypopro" (Fig. 2, hp) and "hyporetro" edge, and the 

 middle lines or the lines of intersection of the three determining 

 planes with the four surfaces mentioned may be called the upper 

 and lower, pro and retro middle line. In the case a structure or 

 edge is oblique as the margins on the chelae for example, it ma^'- 

 be simply designated l^y the word pro or retro. Thus the "marge 

 inferieur" of Simon's terminology, called by Banks "the row 

 behind the fang ' ' and by Montgomery ' ' the posterior margin ' ' is 

 according to my terminology the i?^/romargin ; while the "marge 

 superieur" of Simon or the anterior margin of Montgomery is the 

 Promargin. There can be no confusion if we apply this terminol- 

 ogy consecutively, no matter what the actual position of the limb, 

 if we only remember that each limb has only one plane of sym- 

 metry and that the entire terminology is based on the correla- 

 tion of planes and their homology in the left and right side of 

 the animal. 



/. The Striictiire and the arrangement of hair on the legs 

 of Pholcus phalangoides Fussl. 



Little attention has been paid to the hair covering the legs 

 of spiders. This is deplorable since many a valuable character 

 may still be derived from its study, as the investigations of Dahl 

 on the trichobothria have proven. They are of great help in the 

 separation of families although their value should of course not 

 be overestimated. I do not know whether the hair will even- 

 tually furnish characters of value for the separation into genera, 

 but it has been already applied for the separation into species of 



