300 
LINYPHIIILE. 
Walckenaera atra. PI. XXI, fig. 215. 
Walckenaera atra , Blackw., Linn. Trans., vol. xviii, p. 631. 
— — Blackw., Annals and Mag. of Nat. Hist., second series, vol. ix, 
p. 274. 
Argus ater, Walck., Hist. Nat. des Insect. Apt., tom. iv, p. 508. 
Length of the female, n;th of an inch; length of the cephalo-thorax, ^nd, breadth, 3 ' 5 th ; 
breadth of the abdomen, ^th; length of an anterior leg, ^th; length of a leg of the third 
pair, ^th. 
The two anterior eyes of the four intermediate ones forming the trapezoid are the 
smallest of the eight. The cephalo-thorax is oval, convex, glossy, depressed on the sides, 
which are marked with slight furrows converging towards an indentation in the medial lin e. 
The falces are moderately strong, conical, armed with teeth on the inner surface, and inclined 
towards the sternum, which is broad and heart-shaped. The maxillae incline towards the 
lip, which is semicircular and prominent at the apex. The legs are provided with hairs; the 
two superior tarsal claws are curved and pectinated, and the inf erior one is inflected near its 
base. The abdomen is oviform, thinly clothed with hairs, glossy, convex above, and projects 
over the base of the cephalo-thorax. The colour of this spider is black, with the exception 
of the falces, maxillae, legs and palpi, which are brown, the first two being much the darkest. 
The male is rather smaller than the female, and the anterior part of its cephalo-thorax, 
where the eyes are situated, is prominent but obtuse, with an oblong indentation on each 
side, extending backwards from the lateral eyes. The cubital and radial joints of its palpi 
are short, the latter being much the stronger; the digital joint is oval, convex and hairy 
externally, concave within, comprising the palpal organs, which are highly developed, com¬ 
plicated in structure, with a long, black, very prominent, curved, filiform spine, enveloped in 
membrane, originating about the middle of the outer side, and a short, straight, pointed one 
at their extremity ; their colour is reddish-brown. 
Both sexes of Walckenaera atra, the males having the palpal organs in a perfect state of 
development, were found in May, 1838, under stones in a moist pasture near Llanrwst. 
In the ‘ Transactions of the Linnean Society,’ vol. xviii, p. 632, a conjecture is advanced 
that this species may be the same as the Theridion acuminatum of M. Wider (Museum 
Senckenbergianum, B. 1, p. 232, taf. 15, fig. 11); but w T ell-marked differences in size, 
structure, and colour, plainly show that they are distinct; and a comparison made between 
Walckenaera atra and Argus bicuspidatus, as suggested by M. Walckenaer in his c Hist. Nat. 
des Insect. Apt.’ tom. iv, p. 508, has been attended with a similar result. 
