142 The four Orders of Arachin'da micnira 



from the system, at least for the present, until zoologists have obtained a correct appreciation 

 of the difiereut types through numerous new finds and more thorough study of them. It is 

 probable that, whilst some of these palaeozoic Arachnida will find their places in orders founded 

 on the now living animals, the majority will be found to constitute one or more new orders. 

 But if these are established with undue haste, the result will only be more confusion. 



It may be noted in this connexion that the Geralinitra, which has been found in the 

 Carboniferous formation of Bohemia and Illinois, is well known to be closely related to Thehjphonus, 

 but that, as appears from the list given by Scudder (6, p. 746) and as has been stated in 

 1899 by Pocock (c, p. 216), no form belonging either to Uropygi or to Ricinulei has been found 

 in strata belonging to the enormous interval between that palaeozoic period and the present time. 



In conclusion we wish to say a few words, relating to one point, concerning that group 

 of Orders for which we propose the name of Arachnida micrura. It is well known that the 

 very long " tail " in Scorpiones has an important function, namely that of producing a powerful 

 blow with the poisonous supra-anal hook, which constitutes the weapon of the animal. Similarly 

 the short "tail" (not the flagellum, but the 10th — 12th abdominal segments) of Uropygi most 

 likely has the function of enabling the animal to direct against an attacking enemy the acid 

 which it is capable of emitting from the two glands which open on the anal joint, because 

 according to our investigation these glands (b) are also found in Tartarides. The justice 

 of this view of the functional importance of the " tail " in Uropygi is, we think, corroborated 

 by the feet that in Amblypygi, where the glands are absent, the " tail " is but little developed 

 as such. Nor is it difficult to understand how it may be of value to Araneaj to possess a 

 " tail " of about the same length as the mamilla? which are placed close by ; because the position 

 of anus at the extremity of such a " tail " prevents the mamillse being soiled. That these are 

 placed close together, apparently at the posterior extremity of the abdomen, is an arrangement 

 of such evident utility as to need no further elucidation. The correctness of this view is con- 

 firmed by the fact that the length of the " tail " corresponds moderately well to the mobility 

 and the length of the (upper) mamilke', the "tail" being less developed when the mamilla? 

 are long and rather movable ; and particularl}' by the very striking fact that the " tail " is feebly 

 developed in Liphistius', where the mamilla; — as is well known — are placed far from the posterior 

 extremity of the abdomen. We are not able to point out the functional value of the " tail " in 

 Palpigradi and Ricinulei ; it must be different from what it is in Uropygi. But this does not 

 diminish — in fact it rather increases — the morphological and therefore also systematic weight of 

 this point of agreement between Pedipalpi, Palpigradi, Ricinulei and Aranea^, that they all possess 

 a " tail " which is typically formed by three segments. These four orders are upon the whole 

 closely connected with one another ; one of the sub-orders of Pedipalpi, viz. Amblypygi, approaches 

 most nearly to Aranete, whilst the other sub-order Uropygi, exhibits a series of essential points of 

 agreement with Palpigradi, through Tartarides, and with Ricinulei, through Oxopoei. We therefore 

 think it expedient, before stating the characters of the order of Ricinulei, to sketch the characters 

 of Arachnida micrura, and the main characters of the other orders of this group. We have 



' For further remarks on this jjoint we refer to Sorensen is preserved in the Copenhagen Museum, has always been in 



(./")• so bad a condition that it is scarcely possible to distinguish 



- It will be remembered that this genus, which is remark- the spinning organs even if one is aware of their existence, 



able on account of the firmly chitinized tergites of the Nor, unfortunately, is it possible to decide whether the 



abdomen, was called lAjihistius because Schiodte, who first "tail," which is very indistinct, consists of one or of two 



described it, believed that it was not furnished with spinning segments, 

 organs. The original specimen of L. desultor Sch., wliich 



