242 K. I. POCOCK. 



which ruu obliquely inwards and backwards towards tlie 

 centre of the carapace. The constancy in position of these 

 tendons in the Spiders suggests their homology throughout 

 tlie order, and their origin from the second or the second and 

 third of the larger normal apophyses. Only one such 

 apophysis is developed in Thelyphonus, and this ai-ises a 

 little in front of the second marginal tendon, not behind it 

 as in the Spiders. Interesting, therefore, it is to observe that 

 in Phrynus — a genus in many respects intermediate between 

 Thelyphonus and the Spiders — the apparent homologue of 

 this tendon lies a little farther back than in Thelyphonus, a 

 little farther forwards than in the spiders. It is also noticeable 

 as a peculiarity in Phrynus that in the third tendon, which, 

 for reasons already given, may be regarded as reduplicated, 

 the extra branch takes the same direction as its twin. One 

 other small structural feature bears out the homologies here 

 suggested. This is the presence in many spiders of a trans- 

 verse thickening of the entosternite jnst in front of the fourth 

 marginal apophysis. The posterior bridge of the entosternite 

 in Thelyphonus has exactly the same relations. Similarly 

 the posterior margin of the pharyngeal notch in the Spiders 

 is generally thickened, so as to suggest its correspondence with 

 the anterior bridge in Thelyphonus. As for the ventral 

 apophyses, there cannot be much doubt that the pair passing 

 from the anterior cornua to the basal segments of the second 

 appendages in Phrynus and Thelyphonus are the homo- 

 logues of each other and of the anterior pair, which have the 

 same origin and are affixed to the sternum close to the base 

 of these appendages in the Mygalomorphiu. So, too, must 

 the second apophysis attached to the sides of the pro- 

 sternuin in Thelyphonus represent the second apophysis 

 attached to the sternum opposite the base of the third 

 appendages (first leg) in tiie Mygalomorpha). Thus it 

 IS possible to bring into complete accord the apophyses 

 developed on the doi-sal and ventral sides of the entosternites 

 of the three orders here considered. 



Scarcity of material for comparison secjns to have prevented 



