414 
HORN EXPEDITION—ZOOLOGY. 
APPENDIX. 
(as in Musagetes). In the genus Scytodes, as recently described by Mr. Pickard 
Cambridge, there is a single large blunt spine on the basal point of the palp, which 
rubs over a series of ridges on the mandible. 
In Phlogius crassipes, a spider which is evidently widely distributed over the 
hotter parts of Australia, being found in Queensland and Central Australia, the 
organ appears to be very similar to that figured by Mr. Pocock in Musagetes.* 
The keys or rods are on the basal joint of the palp, and the opposing spines are on 
the mandible. The spines form a prominent dark patch (Pigs. 2 and 5) on the 
outer face of the mandible, and are arranged in somewhat vertical lines, each line 
containing some nine spines, which gradually decrease in size from above down¬ 
wards. The spinous area is bounded below by a distinct rounded ridge, and the 
arrangement of the spines can easily be seen by reference to the figures. Pigui’e 6 
represents a sectional view of the organ, which has been cut across at right angles 
to the length of the basal joint of the mandible, and shows the spines, which form 
a single row. The two sets of long thin hairs on the margin are separated by a 
space into which the strong claw folds down. 
The keys or rods form a still more distinct patch right in the middle of the 
face of the basal joint of the palp, and when both palp and mandible are at rest 
the spines and keys are in apposition. The size of the area and spines may be 
gathered from reference to Fig. 1, in which (drawn under the camera) they are 
magnified eight times. 
The lower edge of the area is convex, formed by the protruding ends of the 
longer keys, which gradually diminish in size and at the upper end pass gradually 
into a series of close-set stiff hairs. These keys have a very definite structure. 
Each consists of two parts—a distal and a proximal—and the two parts are 
flattened out in planes at right angles to one another. 
8een from above the distal part looks thin, whilst from the side (Fig. 4) the 
proximal part resembles a rod and the distal a Hattened-out plate, with a distinctly 
pointed extremity. As they are rubbed across at right angles to their length this 
peculiar double flattening must give considerable rigidity. Their structure will be 
understood from reference to Fig. 3, in whicli four are drawn as seen from above 
and slightly to the side. There are, as shown in Fig. 4, some six series of keys 
ranged one above the other. 
With regard to the function of this organ there is no doubt as to its sound- 
producing capacity. My attention was drawn to it, as previously noted, by 
* Nat. Sci., Jan., 1895, p. 49. 
