The four Orders of Arachnida mierura 143 



already, on an earlier occasion (a, pp. 236, 237), at a time when we had not yet studied Ricinulei, 

 stated that Pedipalpi is the central one of this series of orders, aud our subsequent investigation 

 of Ricinidei has corroborated the correctness of that appreciation. 



Some authors seem to think that Kcenenia may be placed amongst Pedipalpi — an idea which 

 is probably due to the similarity in appearance between it and Thelyphonoidaj. We would there- 

 fore expressly point out that Palpigradi {Kanienia) is the one of those four orders which is the 

 farthest from Pedipalpi ; amongst the families of the latter order Palpigradi approaches most to 

 Tartarides ; but not nearly so much as Aranete approach to Amblypygi. 



We do not propose here to discuss the question whether the order Pedipalpi ought to be 

 maintained as such, or whether it would not be better to erect the two sub-orders which compose 

 it, Uropygi aud Amblypygi, into independent orders. 



We will confine ourselves to pointing out the remarkable fact that the two groups constituting 

 one and the same order, Pedipalpi, not only differ strongly in respect of a matter so essential as 

 the structure of the mouth, but that one of them, the Uropygi, in this respect approaches much 

 more closely to another order, Ricinulei, than to its own companion sub-order, the Amblypygi. 



C. Pars Systematica. 



Arachnida mierura. 



Tibiie pedum et plerumque palporum in patellam et tibiam divisa?. 

 Abdomen ad basin plus minusve constrictum. 



Segmenta abdominalia postrema tria con.stricta, "caudulam" formant. 



Organa respiratoria (si adsunt) e trunco breviore et tracheis constant, qure simplices (i.e. non ramosse) 

 sunt et spira destitute sunt. 



Ordines Arachnidum micrurorum secundum characteres insignissimos sic collocari possunt : 



I. AntenuK triarticulata?, chelataj. Os labro et labio tantum formatum, mandibulis destitutum, 



quod par secundum membrorani sunt pedes gressorii. Pedum trochanteres verticaliter et femora 

 horizontaliter moventur. Organa respiratoria desunt. Segmenta abdominalia undecim; postremum 

 tlagello praaditum ........... Palpigradi Thorell 



II. Antennae biarticulatse, leviter vel vix chelatse. Os mandibulis instructum. Pedum trochanteres 

 horizontaliter et femora verticaliter moventur. Organa respiratoria adsunt : 



A. Antennae non venenosse. Palpi prehensiles. Segmenta abdominalia duodecim ; postremum 

 appendice (operculo anali aut stylo aut flagello) prseditum. Organa respiratoria brevia : tracheae 

 sunt sacci compressi, segmentis abdominahbus secundo et (plerumque) tertio impositi. 



Pedipalpi Latr. 



B. Antennae venenosae. Palpi palpantes. Segmenta abdominalia duodecim (plerumque obsoleta). 

 Organa respiratoria aut brevia traclieis sacciformibus, compressis, aut longiora tubuliformia 

 (plerumque : et sacciformia et tubuliformia), segmentis abdominahbus secundo et (si determinari 

 potest, ad quod segraentum par posterius pertineat) tertio imposita. Organa copulationis 

 maris articulo ultimo palporum imposita. Organa nendi adsunt : mamillae ventrales (2 — 8) 

 abdominis ............ Aranece Sundevall 



C. Antennse non venenosae, chelate. Palpi prehensiles, chelati. Segmenta abdominalia novem, 

 prioribus duobus brevibus. Organa respiratoria sunt tracheas longissimae, e trunco (sacco) 

 brevi orientes. Organa sine dubio copulatoria tarso III maris imposita . Ricinulei Thor. 



