Mr. Blackwall*s Descriptions of new Species of Spiders. 603 



have been made, and that I have had to depend almost entirely on my own 

 resources, my success in this department of zoology has been greater than I 

 could have anticipated. Much of this success must be attributed to the cir- 

 cumstance of having directed my attention more especially to species which, 

 on account of their diminutive size, require for the accurate investigation of 

 their internal structure the employment of optical instruments possessing a 

 high degree of magnifying power. 



In taking the dimensions of spiders, it is important that the relative length 

 of the legs should be ascertained with accuracy. To facilitate this object, I 

 submei'ge the specimens to be examined in spirit of wine till life is extinct ; 

 then removing them to a piece of white card-board, and carefully extending 

 the limbs with a pin, while they are pliable, I take their extent, from the 

 margin of the cephalo- thorax to their extremity, with a pair of compasses, 

 which, on being applied to a scale of inches and parts, gives their measure- 

 ment. 



When exceedingly minute spiders are made the subjects of investigation, it 

 is essential that the sexual organs should be closely inspected, as they afford, 

 by their complete development, an infallible criterion that the animals have 

 attained maturity ; they also present, by their greatly diversified organization, 

 particularly as regards the males, in which sex they are connected with the 

 terminal joint of the palpi, excellent specific characters, the value of which 

 will be duly appreciated when it is recollected that many species so nearly 

 resemble each other in size and colour as to be distinguished by differences in 

 structure only. 



The principal authorities consulted in putting together the materials of 

 which this paper is composed were MM, Latreille, Walckenaer, Hahn, and 

 Koch. 



Class Arachnida. 



Order Araneidea. 



Tribe Octonoculina. 



Family Drassid^. 



Genus Clubiona, Latr. 



1. Clubiona brevipes. Cephalo-thorace saturate brunneo, antic^ marginibus- 



VOL. XVIII. 4 K 



