308 Prof. T. Thorell on Dr. Berthau's 



readers of the work, and consequently that they would not 

 find it difficult to refer an unknown spider (at least a European 

 one) to its respective tribus. Only, the most prominent and 

 interesting forms of exotic spiders then known were mentioned, 

 and an attempt was made to assign to the exclusively exotic 

 families a place in the different tribus, so far as my restricted 

 knowledge of the matter permitted me to do. And when I 

 believed I had determined, in a way sufficient for my purpose, 

 the limits of the six higher tribus, I could, when coming to the 

 lowest, the Tubitelarife, which also is the most polymorphous 

 and therefore most difficult to characterize in few words, re- 

 strict myself to a negative characteristic, viz. that of saying 

 that all the spiders then known " which could not be classed 

 under another tribus " belonged to the Tubitelariee'^. In 

 order to distinguish the Orbitelariae from the E,etitelaria3, only 

 one character of the many given, for instance, by Westring, 

 was, it is true, adduced by me — that, namely, which is taken 

 from the height of the clypeus compared with that of the area 

 formed by the four central eyes, a character which has its ex- 

 ceptions (duly indicated) quite as well as all the other marks 

 adduced by Westring, including even that given by Bertkau as 

 distinguishing his Epeiridaj from his Therididas, viz. the pre- 

 sence in the mandibles of the former group of a so-called 

 basal spot (" Basalfleck"). That there should exist an isolated 

 characteristic always and without exceptions sufficient for 

 the limitation of all the different tribus, I do not believe, 

 and never have believed. 



1. That some of the tribus, as they have been understood in 

 ray above-named work, contain elements that ought to be 

 removed from them, I hasten to admit ; and it is in the first 

 place Dr. Bertkau's merit to have assigned to those alien 

 elements a better place in the system. Thus I unhesitatingly 

 admit that the Eresoidse do not belong to the Saltigradge, and 

 that they probably have their true place in the vicinity of 

 Bertkau's Amaurobiada^, and therefore in the tribus Tubi- 

 telariee (the Palpimanoidaj should probably also be classed 

 under this tribus). I also agree with Dr. Bertkau that 

 Facliygnatha ought to be detached from the Retitelariai and 

 united with the Tetragnathoidaj f, within the tribus Orbi- 

 telarise. Both the E,etitelariae and the Saltigradse may, I 

 think, after this elimination^ be considered entirely natural 

 groups, at least as regards European forms. That not only 

 the Territelariee, but also the Laterigradte and the Citigradas 



* ' On European Spiders,' p. 109. 

 t On this family see further on. 



