Sensorij Hair.s 39 



tatives of the two tribes into which we divide the sub-order, and they agree with each other 

 in the essential features. 



Amongst Laiiiatores we have specially examined Assamia Soreusenii Thor., and found one 

 or two sensory hairs on the upper surface of the terminal tarsal joint of the two first pairs 

 of legs ; they are long, light-coloured, blunt, and very like those found in Pnrcellia as to 

 shape and mode of insertion ; sometimes one similar hair is also found on one of the preceding 

 joints. Besides these hairs three peculiar bristles are placed in a longitudinal row on the 

 upper surface of the last tarsal joint just above the place where it slants downwards to the 

 claw ; the proximal one of these bristles is slightly curved or almost straight, conical, short, 

 and rather thick at the base ; the middle bristle is of similar shape, but a good deal stouter 

 and longer; the last oue is of the same thickness as the middle one, but long. Finally, a 

 few bristles are found arranged in a transverse row on the upper portion of the terminal 

 face of metatarsus just above the insertion of tarsus ; on the second metatarsus we have 

 counted four of them ; they resemble most the middle one of the three bristles on the 

 distal extremity of the last tarsal joint. These two sets of bristles are inserted in the same 

 manner ; they are not placed in calicles, but a broad belt of soft skin surrounds the base of 

 each of them. We entertain no doubt of these bristles being a kind of sensory hairs ; in 

 appearance they differ considerably from those on the upper surface of tarsus, but it does not 

 follow that they have an entirely different function. On the upper surface of the last tarsal 

 joint of the last two pairs of legs we have found a very short and stout conical sensory 

 bri.stle, close in front of the extreme edge of the joint, and a similar but a little longer one 

 on the upper free portion of the terminal face of metatarsus of the same pairs. We have 

 besides examined Cosmetus (Gryne) orensis W. S., which we selected for examination, because 

 within the limits of Laniatores it stands far from Assamia. On tarsus and metatarsus of the 

 first two pairs of legs we found the same two kinds of sensory hairs in the same or nearly 

 the same number as in Assamia. On the upper free part of the terminal face of the third 

 and fourth metatarsus we found a solitary one of the short sensory hairs, but we have been 

 unable to find any such on the last tarsal joint. In the families of Cosmetoidaj and Gonylep- 

 toidse, but not in Assamioidse, the last tarsal joint of the third and fourth pair of legs carries 

 on the upper surface near the end a downwards bent process (" pr. terminalis ") which, at 

 least as a rule, has a couple of long, slightly curved sensory hairs (v. Sorensen, h, PL I., 

 figs. 10, 11), and in these two families we have been unable to find the short conical sensory 

 hair present in Assaviia just in front of the end of the tarsus. 



A general survey of the distribution of sensor}' hairs on tarsus and metatarsus in Opiliones 

 brings out the following characters. Throughout the order the elongated, blunt, light-coloured, 

 somewhat curved sensory hairs occur at least oir a part of tarsus of the first two pairs of 

 legs. In the sub-order Cyphophthalmi no other sensory hairs are found on those divisions 

 of the legs. In Laniatores this kind of sensory hairs is only found on the terminal joint of 

 tarsus,. and besides these the more or less conical hairs are found at the distal extremity of 

 the terminal tarsal joint of the first two pairs of legs, at the distal extremity of all meta- 

 tarsi, as well as at the distal extremity of tarsi of the last two pairs of legs, with the exception 

 that in some families the last-named conical hairs on the posterior tarsi are replaced by hairs 

 on their " processus terminalis." In Palpatores the elongated sensory hairs are found on the 

 distal joints of ail tarsi, but many more on the first two pairs of legs than on the last two 

 pairs ; finally, oue or more of the conical sensory hairs are found at least at the distal extremity 



