XYSTICUS. 147 
Males. 
A. Central process of palpal bulb consisting of two separate branches 
whose points converge, each spur-like branch taking a slightly spiral 
curve. Both spurs from certain positions appear to form a kind of 
forceps . . ... a . . pellax, O. P.-Cambr. 
B. Central process of palpal bulb consisting of a single piece, each branch 
being united in the centre, the points of these diverging and slightly . 
recurved away fromeach other . . . . ....... . « facetus, O. P.-Cambr. 
Females. 
A. Vulva consisting of a deep oval cavity, its sides posteriorly somewhat 
compressed, and more or less straight transversely behind. In the 
centre of the cavity lies a longitudinal carina sloping gradually to the 
floor of the cavity on each side . . . 2. «ew we ew ew ee pellax, 
1. Xysticus advectus. 
Xysticus advectus, O. P.-Cambr. Biol. Centr.-Amer., Arachn. Aran. i. p. 71, t. 9. figg. 12, 
12a4(?)*. 
Type, 2, immature, in coll. Godman & Salvin. Total length 5°75 millim. 
Hab. GuatTEMALA, Chicoyoito (Sarg 1). 
I have no doubt that this immature example is the young of the female of X. pellaz. 
Two adult examples of the latter occur in the collection before me, one of them being 
in company with an adult male of X. pellax, taken at the same time and in the same 
locality. 
2. Xysticus pellax. (Tab. X. figg. 11, 3; 12, 2.) 
Xysticus pellax, O. P.-Cambr. Biol. Centr.-Amer., Arachn. Aran, i. p. 188, t. 17. figg. 14, 
144a,6(¢)’. 
Type d, and gynetype 2, in coll. Godman & Salvin. Total length, g 5°75, 9° 6-25 millim. 
Hab. Mexico, Amula in Guerrero (H. H. Smith1); GuatemaLa, Guatemala city 
(Stol/). 
This form is very closely allied to X. ulmi, C. Koch, from Europe, but in the male 
the bulb of the palpal organs has a thin chitinous plate lying close behind the central, 
process, which is absent in the European form, and the spider is also larger. Although 
there can be no reasonable doubt that the female, of which the vulva is here figured 
for the first time and described in the Table, is identical with the type (2) of 
X. advectus, yet one must refrain from making X. pellax a synonym of X. advectus, 
because the type of the latter is not mature. | 
The difficulties of identifying fully adult forms are sufficiently great, while absolute 
certainty in the case of immature forms is not possible. Hence, when a form not fully 
ut 2 
