484 Mr. Blackwall on undescribed Species of Araneidee. 
the abdomen, +th of an inch; length of the cephalcthorax :,; breadth 
a'y; breadth of the abdomen ;; length of an anterior leg +; length of a 
leg of the third pair 4. 
This spider, which, like Tetragnatha extensa, frequently extends the first 
and second pairs of legs forwards, and the third and fourth pairs back- 
wards, in a line with the body, was found in a cleft of a rail at Oakland, 
in the month of April, 1835. I have not yet seen the male. 
Theridion filipes. 
This remarkable species has the cephalothorax of an oval form; it is con- 
vex and glossy, with an indentation in the medial line of the posterior re- 
gion. Mandibles powerful, conical, armed with teeth on the inner surface, 
rather divergent at the extremities, and inclined towards the pectus, which 
is heart-shaped. Maxillee enlarged at the base, where the palpi are in- 
serted, obliquely truncated on the outer side, at the extremity, and in- 
clined towards the lip, which is semicircular, and prominent at the apex. 
Legs and palpi long, slender, and furnished with hairs and some fine, erect 
spines. These parts are of a brown colour, the mandibles and maxillz 
having a tinge of red. Eyes disposed in two transverse rows on the fore 
part of the cephalothorax; the intermediate eyes of both rows form a 
trapezoid whose anterior side is considerably the shortest; the lateral 
ones are placed obliquely in pairs, each pair being seated on a small emi- 
nevice, and geminated ; the posterior eyes of the trapezoid are larger, and 
the anterior ones much smaller than the rest. Each tarsus is terminated 
by three claws ; the two superior ones are curved and slightly pectinated, 
and the inferior one is inflected near its base. The first pair of legs is the 
longest, then the fourth, the third pair being the shortest. Abdomen oval, 
convex above, projecting over the base of the cephalothorax; it is thinly 
covered with hair, glossy, and of a blackish brown colour, with a tinge of 
olive. A long, slender, cylindrical, semitransparent process, directed back- 
wards, is in connexion with the sexual organs. Plates of the spiracles of a 
deep, dull brown colour. Some specimens have a series of faint, pale, an- 
gular lines, whose vertices are directed forwards, extending along the mid- 
dle of the upper part of the abdomen. 
Length, from the anterior part of the cephalothorax to the extremity 
of the abdomen, 3th of an inch; length of the cephalothorax 5; breadth 
23 breadth of the abdomen +',; length of an anterior leg 2%, ; length of 
a leg of the third pair -3,. 
The male is rather smaller and darker coloured than the female, but the 
relative length of its legs is the same; their absolute length, however, is 
greater, an anterior one measuring }4ths of an inch. The third and fourth 
Joiuts of the palpi are short; the latter, which is the stronger, being pro- 
minent on the inner side and in front; with the frontal prominence se- 
veral long bristles are connected: the fifth joint is of a long, irregular 
oval form, having a projection on the outer side, and two smaller ones on 
the upper part, near its articulation with the fourth joint; it is convex 
and hairy externally, concave within, comprising the palpal organs, which 
are highly developed, complicated in structure, and of a red-brown colour; 
a strong, corneous spine, enveloped in a delicate, transparent membrane, 
originates in the upper part of these organs, and, bending downwards, ex- 
tends along their inner side a little beyond the termination of the fifth 
joint, being curved outwards at its extremity. 
This spider is allied to the Neriene by the disposition and relative size 
of the eyes, and to the Linyphie by the length and delicacy of its limbs ; 
indeed, on a superficial view, it bears a striking resemblance to Linyphia 
pusilla ; but the structure of the maxilla and the relative length of the 
