PULMONARIiG. 163 



extends along the back, and gives off branches on each side 

 and anteriorly(l). There are always eight legs. The head 

 is always confounded with the thorax, and presents at its 

 anterior superior extremity two mandibles — -so called by 

 authors, the chelic.erse or antenne-pinces, Latr. — terminated 

 by two fingers, one of which is movable, or by a single one 

 resembling a hook or claw that is always movable(2). The 

 mouth is composed of a labrum(3), of two palpi, sometimes 

 resembling arms or claws, of the two or four jaws, formed, 

 when there are but two, by the radical joint of these palpi, 

 and moreover, when there are four, by the same joint of the 

 first pair of feet, and of a ligula consisting of one or two 

 pieces(4). If we base our arrangement on the progressive 

 decrease of the number of pulmonary sacs and stigmata, the 

 Scorpions where it is eight, while in the other Arachnides 

 it amounts to but four or two, should form the first genus of 

 this class, and consequently our family of the Pedipalpi should 

 precede that of the Araneides(5). But the latter Arachnides 



( 1 ) According- to Marsel de Serres,Memoire sur le Vaisseaii Dorsale des Insectes, 

 the blood, in the Araneides and Scorpions, is first directed to the organs of respira- 

 tion, and thence proceeds to various parts of the body through particular vessels. 

 Judging-, however, from the affinity of these animals to the Crustacea, the circula- 

 tion would seem to be effected in the contrary direction. See the Memoir of 

 Treviranus on the Anatomy of Spiders and Scorpions. 



(2) These parts are formed of a first very large and ventricose joint, one of 

 whose superior angles, when the chelee are didactyle, forms the fixed finger, and 

 of a second joint, that which forms the opposite and movable finger or the hook, 

 when tliere is but one finger. In the latter case, as with several of the Crustacea, 

 I will employ the term claw. 



(3) See our general observations on the class. 



(4) That of the Scorpions appears to be composed of four pieces, forming an 

 elongated and pointed triangle, directed forwards; the two lateral ones however 

 are evidently formed by the first joint of the two anterior feet, and may be con- 

 sidered as two jaws analogous to the first. We see by My gale, Scorpio, &c. that 

 the palpi are divided into six joints, of which, in the other Araneides, the first or 

 radical one, is anteriorly and internally dilated to form the maxilliform lobe. Even 

 this lobe, in some species, is articulated at base, and thus becomes a maxillary 

 appendage of this same joint. Exclusive of this joint, the palpus consists of but 

 five, and such is the most usual mode of supputation. In the Scorpions the 

 movable finger of the forceps, as in that of the Crustacea, forms the sixth joint. 



(5) In my Fam. Nat. du Regne Animal, 1 begin with the Pedipalpi. M. Leon 

 Dufour also thinks that the Scorpions should come first. 



