170 
Psyche 
[June 
allow separation from A. hadros because of the relatively long meta- 
tarsus I of A. river si. The cheliceral apophysis is relatively thinner 
than in A. hadros and most specimens of A. gertschi (see CAT and 
CAT/CL, Table I). Females. The form of the seminal receptacles 
and bursa copulatrix aids in distinguishing this species from the 
others (Figs. 80-86). IVML/IML is smaller for A. riversi than 
for the others (Table II) because of the relatively short metatarsus 
I of A. hadros and the relatively long metatarsus IV of A. gertschi. 
geographic variation. Males. Comparisons of coastal popula- 
tion samples ( A , B , C, D, E and F) with one another and com- 
parisons of Sierran population samples (G, H and I) with one an- 
other usually yielded smaller “distances” than coastal sample vs. 
Sierran sample comparisons for the same character. Sierran males 
are generally smaller than coastal males, but there is considerable 
overlap (Fig. 22). Many other measurements and meristic char- 
acters are correlated with body size and showed patterns of geographic 
variation similar to that of CL, but a few (IFL, ITarL, PFL and 
PTL) showed less or no overlap between Sierran and coastal samples 
(Figs. 23, 24). These appendage segments are relatively longer in 
the coastal samples (Fig. 23). Ratios formed of all other leg seg- 
ment lengths over CL result in very wide overlap between Sierran 
and coastal samples. The palpal tibia is relatively more swollen in 
Sierran males than in coastal males (Fig. 24). Pedipalp figures 10 
13 illustrate this variation. 
Explanation of Plate 9 
Figs. 22-29. Geographic variation in A. riversi. (All measurements in 
mm. For scatter diagrams solid black dots represent Sierran specimens, 
open dots coastal specimens, and X’s the two Sierran foothills specimens.) 
22-24. Males. 22. Modified Dice-Leraas diagram of CL variation. (Hori- 
zontal line represents the observed range, vertical line the mean, open 
rectangle the standard deviation, solid black rectangle the 95 percent confi- 
dence interval for the mean, number to right of range line the number of 
specimens in the sample, and letter in left column the sample-locality.) 23. 
Scatter diagram of IFL plotted against CL. 24. Scatter diagram of PTT 
plotted against PTL. 25-29. Females. 25. Mod. Dice-Leraas diagram of CL 
variation. 26. Histogram of CMT. (One unit of vertical scale equals a 
single chelicera.) 27. Mod. Dice-Leraas diagram of CMT/ICTR varia- 
tion.. Two dots above sample G symbol represent the two Sierran foothills 
specimens. Top two symbols represent variation in entire coastal sample 
and entire Sierran sample. 28. Scatter diagram of SW plotted against CL. 
29. Mod. Dice-Leraas diagram of ITL/CL variation. 
