44 ON NEW AND RARE ARACHNIDS. 



Oxyptila sanctuaria, Cambr. 



Several adult males at Warmwell Rectory by Rev. R. J. 

 Pickard-Cambridge on Oct. 5, 1910. 



Sub.-Fam. PHILODROMIN^. 



Genus TIBELLUS, Simon. 

 Philodromus, Walck., ad partem. 



Dr. Jackson has called my attention to the fact that we 

 have two different forms in our British collections of 

 Tibellus oblongus, Bl.-Walck, namely, Tibellus oblongus, 

 Walck. -Kulczynski, and Tibellus parallelus, C. L. Koch- 

 Kulczynski. These two forms so nearly resemble each 

 other in general appearance, colour, markings, and habits 

 that it is not extraordinary that they have been hitherto 

 confused ; the chief point of difference in their structure 

 being confined to the palpal organs of the male and the 

 form of the genital aperture of the female, all of which 

 require a somewhat microscopic power to differentiate 

 satisfactorily. The difference between the above- 

 mentioned portions of structure will be seen at a glance 

 from the figures given in the plate, but after a considera- 

 tion and close examination of a long series of specimens 

 from my own and correspondents' collections, I have 

 come to the conclusion that the two forms we have may 

 be also distinguished in both sexes by markings on the 

 abdomen, i.e., by the more or less distinct presence of two 

 black spots, one on each side of the posterior half of the 

 upper side about a third of the length from the hinder 

 extremity. In some examples there may be other black 

 spots, or rather dots, in the same longitudinal lines, but in 

 those cases the two critical ones mentioned are always most 

 pronounced and easily observed. The presence of these 

 two spots, it seems to me, marks the Tibellus parallelus of 



