In general appearance, colours, and markings this spider bears great resemblance to N. cæmentaria. The eyes, however, appeared to be smaller, and the hind-centrals also smaller in proportion to the rest. The pale margins of the cephalothorax are in the present species generally confined to some rather indistinct pale patches.
The central orange band from the eyes to the thoracic fovea is, especially in immature examples, often only a simple tapering line; in others it is larger, and often composed of three converging narrow orange bands, which form, in some examples, a broad central tapering band, marked with two longitudinal dark lines. The thoracic fovea is curved, but not sharply.
The abdomen is broadish oval, of a dull clay colour, marked with dark brown lines, and markings on the sides and upper side. In some examples these form a longitudinal central series of curved or slightly angular lines; in others but little trace of regular chevrons can be seen.
In the present spider there is also a longitudinal pale yellowish patch on the inner upper margin of the falces near their base; they are furnished with hairs in longitudinal bands, and spines, like others of the genus.
The legs are moderately long, strong, and furnished with hairs and bristles, and, sparingly, with spines. The genual joints of the third pair have some spines on the outer side, varying from one to three in different examples. The tarsi and metatarsi of the first and second pairs, as well as the radial and digital joints of the palpi, have strong lateral brush-like fringes of close-set sooty black hairs. The superior pair of tarsal claws are denticulated, but not uniformly either in strength, number, or position.
No doubt this will prove a very troublesome spider to distinguish with certainty from N. cæmentaria, but the almost constant presence of a spine or spines on the outer face of the genual joint of the third pair of legs seems to be a good distinguishing character; in no one example out of nine carefully examined could I detect their absence altogether, while a single spine even on N. cæmentaria is rare.
In the present species five examples had three spines on each of these joints; two had two spines on each; one had a single spine on each; another had one on one side, two on the other.
The nest, however, is very characteristic and peculiar. It is of the wafer-lid type, and so cannot, from even the outside, be mistaken for that of N. cæmentaria, which is of the cork-lid type; it is, moreover, branched below, while that of N. cæmentaria is a single unbranched tube. It has also an inside door, or valve, of very remarkable construction, having two perfect cork-like faces, securely shutting off either the branch, or the main tube just above the branch, at pleasure. By this latter character it is distinguished also from the tube of N. Manderstjernæ, as well as by the absence of a second short branch or cavity, lately discovered in the nest of this last spider. Examples of this spider were found, not unfrequently, but invariably in such nests as that above described, at Hyères.
The female sex only has yet been met with.
Habitat. Hyères.