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Art. VI T. — On the Pedipalpi of North America.'^ 



By Horatio C. Wood, Jr., M. D. 



Ord. PEDIPALPI. 



Respiratio pulmonavia. JMasillre maxima!. Maxillarum palpi maximi a " maiiu" tcrminati. 



Among the Pcdipalpi the ccphalothorax is always covered witli a dorsal shield 

 entirely separate from the abdominal scuta. In the Scorpionidaj the abdomen is 

 continuous with the cephalothorax, whilst in the Thelyphonidas and PhrynidiV! they 

 are united by a pedicle. In the first family the abdomen is prolonged posteriori}^ 

 into a sting-bearing appendage or tail. In the second there exists merely a filiform 

 prolongation, which is in the third, still further degenerated into a mere button. The 

 ScorpionidfB have the foremost feet well developed as such. In the Thelyphonidoe 

 they are very slender and strikingly elongate. Whilst in the Phrynidte they are ex- 

 cessively long, filiform, and multiarticulate, indeed, almost moniliform. The Scor- 

 pionida? are provided with the so-called " combs," which are wanting in the other 

 families. These are situated just behind the legs, one on each side of the genital 

 opening. Their function is not exactly known — but is probably connected with 

 the sexual act. 



The most anterior of the organs connected with the mouth, in the Pedipalpi are the 

 mandibles, the " antennes pinces " of Emile Blanchard. Their analogy and 

 homology with the mandibles of Coleoptera are very obvious. In the ScorpionidtB 

 they are formed of two corneous joints. Of these tlie posterior is very small ; but the 

 anterior is much larger and armed with both a moveable and fixed finger. The former 

 is so articulated as to have its motion in a horizontal plane, and has its inner surface 

 generally deeply grooved with denticulate margins. This channel receives into 

 itself the dentate edge of the fixed finger. Among the Thelyphonidse and Phrynidte 

 the first joint is wanting. The second is large and somewhat cuneate. Its lower 

 edge as well as the fingers are generally hidden by very thick crests of long silky hairs. 

 The movement of the upper finger is in a vertical plane. Their whole appearance re 



*This paper is founded, almost entirely, on specimens belonging to tlie Smithsonian Institution. For the 

 privileo-e of investigating them, we would offer our thanks to Profs. Henry and Baird. For the same reasons 

 as before influenced us, we do not consider Mexico as included in our scope. 



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