1897.] i a. R. I. POCOCK ON ETHIOPIAN SPIDERS. 743 



the young stages of a species in which, when adult, the pads are 

 complete, that is show no median divisional line of normal hairs, 

 be examined, it will be found that at- first the tarsi are clothed 

 with setae, and these later on become intermixed with scopular 

 hairs. As the animal increases in size the scopular hairs increase 

 in number, gradually spreading over the tarsus, and apparently 

 replacing the normal setae. But the replacement does not take 

 place at a uniform rate all over the foot ; on the contrary, the 

 pad, beginning at the sides, encroaches by degrees inwards, and, 

 as a consequence, the last part to remain unoccupied is the middle 

 line of the sole, which retains longest its primitive clothing of 

 setse. In the second place, it will further be noticed that the 

 tarsal pads do not reach their full development contemporaneously, 

 the order of their appearance corresponding with the order of the 

 legs from before backwards — the first tarsus being covered before 

 the second, the second before the third, and the third before the 

 fourth ; so that when the pads upon the first or second legs are 

 complete, those on the fourth, or even the third, may still retain 

 their divisional line " . . . " Hence it follows that the division of 

 the scopulaB may he nothing but a sign of immaturity . . ." and a 

 species belonging to section a" for example of the above table 

 " will in its early days fall into the Ischnocoleae, a little later into 

 the Chaetopelmateffi, then into the Crypsidromeae." 



Nevertheless, species undoubtedly exist in which one or all of 

 the tarsi retain throughout life the divisional band of setse ; but a 

 study of such of these genera as have been available has convinced 

 me that the groups based upon such a character are largely 

 artificial, and that in a natural classification of the family, within 

 one and the same group genera will be found either with all or 

 none of the tarsal scopulae divided ; a conclusion which might be 

 expected if the law of the growth of the tarsal scopu]a3 mentioned 

 above be true. For the genera that present a band of setae on 

 the scopulae are merely a little less specialized than those that lose 

 them. It is, moreover, interesting to observe that in this character 

 the adults of species of small size often resemble the young of 

 closely-allied but larger-sized species. 



In another paper ^ I endeavoured to show that most of the 

 genera inhabiting the Oriental region fall into two families, named 

 respectively the Ornithoctonidae and Selenocosmiidae ; but it has 

 since appeared to me advisable to reduce these to the rank of 

 subfamilies, and term them Ornithoctoninae and SelenocosmiinEe. 



These subfamilies are based upon the possession of a pecuHar 

 form of stridulating organ lying between the mandible and maxilla, 

 but the organ is quite different in the two groups. The genera 

 presenting these organs also agree in a number of other features, 

 not, however, sufficient in themselves to differentiate them from 

 some of the African genera. 



The Selenocosmiinse contain the genera referred by Simon to 



1 Ann. Mag. Nat. Hist. (6) xv. pp. 165-184 (1895). 



