Locomotory Limbs 29 



generally have tarsi consisting of many joints ; similarly Oncopus Tlmr. lias undivided tarsi, 

 though tarsi are generally divided into several joints in the sub-order Laniatores, to which 

 Oncopodoidw belong; albeit the number of tarsal joints is less in Laniatores than in the 

 majority of Palpatores. But there is another point in which Cyphophthalmi strikingly differ 

 from other Opiliones. In the other sub-orders the artit.ulation between metatarsus and 

 tarsus admits of more or less considerable movement. It is very considerable in Laniatores 

 and those Palpatores whose tarsi are divided into a limited number of joints, and in these 

 animals the tarsus can be bent somewhat upwards, so that the dorsal line of tarsus con- 

 stitutes an obtuse angle with that of metatarsus. The movement is less considerable in 

 Palpatores with many-joiuted tarsi, but here the tarsus itself is capable of being 

 curved so that its dorsal line becomes somewhat concave. These structural features 

 are in accordance with the fact that the animals of these two sub-orders tread on the 

 under surface of their tarsi, either on the whole under surface, viz. in Laniatores and in 

 Palpatores with tarsi consisting of a limited number of joints, or on the under surface of the 

 last joints of tarsus, viz. in Palpatores with tarsi composed of many joints. In Cyphophthalmi, 

 on the contrary, the articulation bebwecu metatarsi and tarsi is, as we have pointed out, 

 flexible only to a very small degree, and only downwards (not upwards as in Trogulus or 

 Laniatores), which is connected with the fact that these animals manifestly tread only on the 

 ends of their tarsi, at least with the three posterior pairs of legs. (This opinion was commu- 

 nicated to Dr. Purcell, who verified it after observation on Purcellia.) It is also in perfect 

 accord with this fact that the spines, which like those on the legs of Insects serve to push 

 off with in walking, are altogether absent in Cyphophthalmi on metatarsus as well as on 

 tarsus. In Laniatores, excepting Oucopodoidse, there are always a pair of spines, serving as 

 spurs, at the distal extremity of metatarsus. Palpatores vary in this respect : many Phalan- 

 gioidse possess a pair of such spurs at the ends of the proportionally longer tarsal joints, 

 whilst the most distal shorter ones are without them; but not a few genera have no such 

 spines either on metatarsi or on tarsi, such as Troguloidse, Nemastomatoidse, and even certain 

 genera of Pbalangioidse, for instance Sclerosoiiia. Even in these, however, the hairs on the 

 under surface of tarsi are much more stiff than those which occur on the under surface of 

 tarsi in Cyphophthalmi. We implied just now that the tarsi of the first pair of legs form 

 an exception, though perhaps not in the whole family of Sironoidaj. It will readily be 

 seen fiom PI. III., figs. 2 /* and 3 d ; PI. III., fig. 1 /, and PI. II., fig. 4 c, that in Pettalus, 

 Ogovia, and StyloceUus, particularly in S. Focockii u. sp. (PI. II., fig. 5 d), the distal portion 

 of tarsus of the first pair of legs is distinguished by greater thickness than the rest along a 

 greater or smaller part of the under surface, and that in this place there is a peculiar covering 

 of fine perpendicular hairs standing close together and of almost equal length, which is not 

 found either on the dorsal side or on the basal portion of the under side of this tarsus, any 

 more than it is on any of the other tarsi. It can scarcely be doubted that the animal treads 

 on this part of tarsus, and it must be admitted to be to some extent iu accord with the fact 

 that in Sironoidse the first pair of legs is generally longer than, rarely as long as or slightly 

 shorter than, the fourth, always longer than the second and third pairs, and notably thau the 

 second ; because in the other sub-orders of Opiliones the first pair of legs is always the shortest, 

 and more particularly shorter than the second, which is the longest pair in Palpatores, whilst 

 the fourth is the longest in many Laniatores. The portion of tarsus just described is conspicuously 

 thicker than the remainder in Pettalus, Ogovia, and StyloceUus Pocockii, but in the other 

 species of Stylucellus this is the case only to a small extent, for instance in >S'. Beccarii 



