Olfactory Organs of Spiders. 331 



number of the auditory hairs upon the tibia?. There exist 

 four in one row, whereas usually in the Theridiidae the 

 number three is not exceeded. Steatoda indeed constitutes an 

 exception on the one side ; and on the other, among the Epei'- 

 ridte, the number is less in Singa and Cercidia. 



II. The tarsus not with a 7'udimentary auditory cup ^ seldom 

 quite without auditory hairs (Dysdera), usually, as well 

 as the metatarsus and tibia, with a considerable number. The 

 cups in this group are much less characteristically developed. 



Terr{teJari(je. — Unfortunately of this group I had no fresh 

 examples at ray disposal, and on the spirit-specimens of the 

 zoological collection in Kiel, which Prof. Mobius kindly made 

 over to me for examination, the auditory hairs were for the 

 most part broken off. So much, however, appeared to be 

 certain, that here a considerable number of rather irregularly 

 placed hairs exists upon the last joints of the limbs. If this 

 be correct, the group stands in this respect in opposition to all 

 other spiders. 



The Dysderidffi are distinguished by the small number of 

 their auditory hairs ; here there exist only one or two upon 

 the tibiae, upon the metatarsus one, and upon the tarsus one 

 only in Segestria, while there is nothing of the kind in either 

 Dysdera or Harjjactes. 



In all (he other families there is a considerable number of 

 auditory hairs upon all the three terminal joints of the limbs. 

 But according as there are one or two rows upon the tarsus, 

 we can again distinguish two groups here : — 



1. With one row of auditory hairs upon the tarsus : — 

 Amaurohiidoi, Agalenidoi, Phihdromida'^ Thomisidce, and 

 Attidm. 



2. With two rows of auditory hairs upon the tarsus : — 

 DrassidcBj A nyphcBuidce, and Lycosidce. Among the Drassidse, 

 however, the two rows are sometimes very close together (e. g. 

 in Prosihesima), In Argyroneta also, in which the auditory 

 hairs in general differ less from the rest, it is difficult to say 

 whether we have before us one or two rows. 



Systematically the position of the auditory hairs, especially 

 in the first group, may be employed much more extensively 

 for distinguishing genera and species ; but upon this I cannot 

 here go into details. 



As already mentioned, the development of the cup especially 

 differs in completeness. Besides the character given, the 

 first group is distinguished by the very characteristic form of 

 this cup ; hence the animals of this group are specially fitted 



