Many of the spiders from the rocks are so fragmentary that it is impossible to decide with certainty on their systematic position, but a considerable number of them—more than half—have been assigned to recent genera.

The amber spiders are mostly well preserved, and can be classified with more certainty. Many of them are surprisingly like existing forms, though others, like Archaea paradoxa, differ greatly from most spiders now extant, though they show some affinities with one or two remarkable and aberrant forms.

CHAPTER XV
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—ARANEAE (CONTINUED)—CLASSIFICATION

The systematic study of Spiders has hitherto presented very great difficulties. There is an extensive literature on the subject, but the more important works are costly, not commonly to be found in libraries, and written in diverse languages. Moreover, the nomenclature is only now emerging from a condition of chaos. Able and diligent Arachnologists have done admirable work in studying and describing the Spider fauna of their various countries, and occasional tentative suggestions have been put forth with a view to reducing to some sort of order the vast mass of heterogeneous material thus collected. Most schemes of classification, based chiefly upon a knowledge of European forms, have proved quite inadequate for the reception of the vast numbers of strange exotic species with which recent years have made us acquainted. The number of described species is very large, and is rapidly increasing; but though we are very far indeed from anything like an exhaustive knowledge of existing forms, it may now be said that almost every considerable area of the earth’s surface is at least partially represented in the cabinets of collectors, and it is possible to take a comprehensive view of the whole Spider fauna, and to suggest a scheme of classification very much less likely than heretofore to be fundamentally deranged by new discoveries.

The first to apply the Linnaean nomenclature to Spiders was Clerck, in his Araneae Suecicae (1757), which gives an account of seventy spiders, some of which are varieties of the same species. A few new species were added by Linnaeus, De Geer, Scopoli, Fabricius, etc., but the next work of real importance was that of Westring (1861), who, under the same title, described 308 species, divided among six families. Blackwall’s beautiful work, the Spiders of Great Britain and Ireland, was published by the Ray Society in 1864. He divides spiders into three tribes, Octonoculina, Senoculina, and Binoculina, according to the number of the eyes, and describes 304 British species, distributed among eleven families.

His successor in this country has been Pickard-Cambridge, whose work, under the modest title of The Spiders of Dorset (1879–81), is indispensable to British collectors.

Blackwall’s division of the order into tribes was evidently artificial, and has not been followed by later Arachnologists. Dufour (1820) founded two sub-orders, Dipneumones and Tetrapneumones, based on the presence of two or four pulmonary sacs. Latreille (1825) established, and many Arachnologists adopted, a division into tribes based upon habits, Orbitelariae, Retitelariae, Citigradae, Latigradae, etc., and this method of classification was followed in the important work of Menge, entitled Preussische Spinnen, which was published between 1866 and 1874.

Since 1870 determined efforts have been made to grapple with the difficult subject of Spider classification, notably by Thorell and Simon. The latter, undoubtedly the foremost living Arachnologist, writes with especial authority, and it is inevitable that he should be largely followed by students of Arachnology, who cannot pretend to anything like the same width of outlook.

It is indicative of the transition stage through which the subject is passing that Simon in his two most important works,[[306]] propounds somewhat different schemes of classification, while in the Histoire naturelle, where his latest views are to be found, he introduces in the course of the work quite considerable modifications of the scheme set forth in the first volume.

In that work the order is divided into two sub-orders, Araneae theraphosae and Araneae verae, the first sub-order containing Liphistius and the Mygalidae or Theraphosidae of other authors, while all other spiders fall under the second sub-order. The Araneae verae are subdivided into Cribellatae and Ecribellatae, according to the presence or absence of “cribellum” and “calamistrum” (see p. [326]) in the female. Important as these organs doubtless are, the Cribellatae do not appear to form a natural group, some of the families having apparently much closer affinities with certain of the Ecribellatae than with one another. This is especially evident in the case of the cribellate Oecobiidae and the ecribellate Urocteidae (see p. [392]), which most authors unite in a single family.