164 Mr. A. Tulk on the Anatomy of Phalangium Opilio. 



of the joints are thus distinctly circumscribed, with the exception 

 of the last. The apices of the two posterior pairs of coxae abut 

 against the sides of the sternum ; the third, shorter than the rest, 

 has the elongated appendage already described in front, and the 

 most anterior pair support the second pair of jaws. The articular 

 cavity presents, inferiorly, an oblique crescentic margin, to which 

 the ligament attaching the second joint is fixed. The upper half 

 of the margin is straight, and has in the centre an acute spine 

 directed outwards. The second joint or trochanter, which arti- 

 culates with the preceding by ginglymus, is of small size and 

 somewhat quadrate in form. It is more convex below than above, 

 and shorter in the reverse direction, owing to the oblique position 

 of the articular openings. The sides of the distal extremity are 

 prolonged into a short spine, and the margin of the proximal 

 cavity presents in the centre, inferiorly, a blunt, flattened and 

 conical projection. A dark impressed line extends from the distal 

 end of the joint to nearly half the length of the upper surface. 

 The third joint or femur, long and slender, has rows of spines, 

 with short bristles intervening between them, disposed longitudi- 

 nally over it ; its inner extremity is slightly dilated, and pro- 

 longed obliquely into a conical shape. The external has an ob- 

 lique articular cavity, for the reception of the fom-th joint, or first 

 portion of the divided tibia, which, with the second, is constructed 

 upon the same general plan with the femur, only it is much 

 shorter. To the above joints succeeds a long, filiform and multi- 

 articulate tarsus. The first joint is the longest, and from this 

 they gradually diminish in length towards the extremity of the 

 tarsus, where they become nearly globular. They are fringed 

 upon either side with close-set hairs, directed obliquely down- 

 wards, and their anterior angles are furnished with a strong 

 spine. The last joint is oblong in form, and supports a single 

 curved and moveable hook. The following is the number of 

 joints, commencing with those of the anterior tarsi : — 1st, 37 

 joints j 2nd, 7Q joints j 3rd, 35 joints ; 4th, 38 joints. Total for 

 all the tarsi, 372 joints. 



DESCRIPTION OF PLATE III. 



Fig. 1, The body of a Phalangium Opilio^ as seen from its upper surface. 



Eight only of the dorsal segments are visible. 

 Fig. 2. The same, from below. In both views the legs have been removed 



at their articulations with the coxae, leaving only the latter attached 



to the cephalo-thorax. 

 Fig. 3. An antero-inferior view of the cephalo-thorax, exhibiting the cheli- 



cerae drawn apart to show their vertical septum, the epipharynx 



and labrum, I; the first and second pair of maxillae, with the palpi 



and first pair of coxal joints. 1 . 

 Fig. 4. A side view of the septum, epipharynx and iabrum, detached. 

 Fig. 5. External view of the right chelicera, to show the basal joint of the 



maxillary palpus, prolonged inwards at i, to form the first pair of 



jaws. 



