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Show 18/5.]] NEW SPECIES OF ERIGONE. 191 that very many more remain to be discovered; and the number of curious and distinct conformations of the caput in the male would seem to be almost without limit. It is probably from tbe several distinct types of this portion of the structure that'it will be found some day most practicable to break up the genus into subordinate groups. While, however, the males may be thus grouped, it appears as yet that the females do not follow the same laws of development in respect of the caput, the structure of that part in the female affording frequently no evidence at all of affinity to tbe male; hence arises the great difficulty, in very many cases, of deciding to which species the females belong; for it often happens that any one of several females may, as far as structure and colour are concerned, be, with equal propriety, relegated to one male. It is not difficult to distinguish the different females among themselves, since each ordinarily possesses strong specific characters ; but their general similarity of form makes it exceedingly difficult to propose any method of grouping them. ERIGONE RETROVERSA, sp. n. (Plate XXVII. fig. 1.) Adult male, length 1^ line. The cephalothorax of this very distinct species is of a dull greenish olive colour and of a rather flattened form, the caput and thorax being nearly on the same level, and the normal grooves and indentations indistinct; the height of the clypeus is not quite two thirds of that of the facial space. The eyes are of moderate size and not very unequal in their relative magnitude ; they are seated on the fore part of the caput, which projects slightly forwards, in two transverse rows or four pairs somewhat closely grouped ; those of the hinder row are about equidistant from each other, those of the fore central pair, which are the smallest of tbe eight, are rather nearer together than each is to the fore lateral eye on its side. " The legs are of a pale yellow colour, the tibiae of the first and second pairs being dark olive-brown; they are long and strong, furnished with hairs and a few nearly erect slender spine-like bristles. The palpi are short: the cubital and radial joints very short, but of about equal length ; the former is somewhat subangularly prominent on its upperside, where it has a strong, black, tapering bristle ; a similar but longer and stronger bristle springs from the upperside of the radial joint, which enlarges at its extremity, but has no prominences or projections : the digital joint is of a dark yellowish brown colour, and has its hinder extremity produced into along, very strong and slightly tapering projection, which curves back towards the cubital joint; the length of this produced part is equal to that of the joint, and its extremity is somewhat squarely truncated and of a blackish colour; near the extremity, on its outer edge, is a strong, black, sharp pointed corneous prominence; and below this again the digital joint has a large curviangular prominent lobe; the palpal organs are well-developed, prominent, and complex. The falces are long, strong, and a little inclined backwards ; they are similar in colour to the cephalothorax. |