446 Mr. T. II. Savory on the Spider Llpliistius. 



the spiiuierettes aro placeil in the middle of the lower surface, 

 a place which is obviously more closely allied to the normal 

 position of the abdominal appendages of the Arthropoda. 

 All other spiders have six, or fewer, spinnerettes, while 

 Liphistius alone has eight. The significance of these facts 

 needs no emphasis. 



The segmentation of the abdomen is equally striking. 

 This part of the body is protected by a series of nine dorsal 

 ))lates of a leatliery consistency, a fact which points to a rela- 

 tionship between the Araneaeand the Pedipalpi and Scorpions. 

 Simon suggests that these plates may not represent segmenta- 

 tion, but that they may result from the division of a dorsal 

 shield, such as is found in the Oonopida3 and the Tetra- 

 blemma. This is one of the points which it is hard to solve 



Fiir. 1. 



ProEle. 



in the absence of embryological knowledge ; analogy is apt 

 to prove misleading, but the following arguments in favour of 

 their primitive nature may be cited : — 



1. The fossilized spider, Protolj/cosa, of the Carboni- 



ferous strata possesses a similar series of dorsal 

 plates. 



2. Some species of the genus Paratropis, one of the 



more generalized Therapliosa?, show vestiges of 

 nine segments in the abdomen of the adult. 



3. Since the abdomen of such spiders as have been 



embryologically studied passes through a segmented 

 stage it is reasonable to suppose that the segmented 

 form is primitive, and on this account the dorsal 

 shield of Oonopides is simply to be regarded as 

 having, like the rest of the abdomen, lost its 

 metamerism. 



