330 M. F. Dahl on the Auditor!/ and 



I. Tibia with two rows of auditory hairs, metatarsus with 

 only one hair, aud the tarsus with a ciq) withotd hairs. 



Upon this it is to be remarked that tlie auditory hair is 

 wanting upon the metatarsus of the fourth pair of legs*, and 

 that one of the rows upon thetibiai sometimes consists of only 

 a single hair, as, for example, upon the anterior tibise of 

 Erigone pusiila^ Wid. The rudimentary cup upon the tarsus 

 seems to be most characteristic of this group, and I think 

 that a special importance must be attached to it in a natural 

 grouping, because, as a rudimentary organ, the cup has very 

 probably no longer a purpose to serve in the animal, and there- 

 fore directly indicates relationship. The rudimentary cup 

 occurs in the following families : — Epeiridge, Uloboridge, The- 

 ridiidee, and Pholcidai. Of the Uloboridaj I have unfortu- 

 nately been able to examine only Hyptiotes paradoxus j C. K., 

 and even of this only a rubbed specimen, so that I recog- 

 nized its belonging to this group only from the small cup 

 just before the middle of the tarsus. The position of this 

 family among the Orbitelarite, which had already been 

 selected on account of the form of the net, is completely con- 

 firmed by this character. An instinct so specially developed 

 as the weaving of the peculiar geometric web is indeed as 

 important as an organ, it being extremely improbable that so 

 singular an instinct could be developed independently in 

 different animals. 



In accordance Avith my division into two groups, I am led 

 to separate the genus Phyllwca, established by me f, from the 

 Agalenidse, and to refer it to the Theridiidre, although several 

 other characters would seem to justify the former position. 



In Pachygnatha and Tetragnatha there are auditory hairs 

 upon the femora also, and, indeed, hitherto I have found them 

 in this position only in those genera. They stand in two 

 rows near the base. This fact confirms the relationship of 

 the two genera, already deduced from other characters by 

 Bertkau %. I therefore, after his example, group them 

 together as Pachygnathidfe in the same family, and refer this 

 to the Orbitelarife. Thus, as in all other groups, so also 

 among the Orbitelaria?, we should have a genus which has 

 exchanged net-weaving for a free mode of existence. Pachy- 

 gnatha further approaches the Epeiridte also in the greater 



* The genus Zilla seems to be the only exception. 



t Schr. d. naturw. Ver. fiir Scblesw.-Holst., Bd. v. p. 61 ; and ' Analy- 

 tische Bearbeitung der Spinnen Norddeutscblands,' Kiel (1883), p. 49. 



\ Bertkau, " Versuch einer natiivlichen Anorduung der Spinnen," in 

 Arch, fur Naturg. (1878). 



