306 AUACHNIDES. 



and they are situated near the base of the abdomen. The number of 

 ocelli is at most but four. They constitute our second and last order, 

 or that of the TKACHEARI^E. 



ORDER I. 



PULMONARY. 



WE here find a well marked circulating system and pulmonary sacs, always 

 placed under the abdomen, announced externally by 

 transverse openings or fissures (stigmata), of which 

 there are sometimes eight, four on each side, and at 

 others four, or even two. The number of ocelli is 

 from six to eight, while in the following order it never 

 exceeds four, and is most generally but two; sometimes 

 they are hardly perceptible, or even annihilated. The 

 organ of respiration is formed of little lamina). The 

 heart is a large vessel which extends along the back, 

 and gives off branches on each side and anteriorly. 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 chelicercc 

 of Latreille, terminated by two fingers, one of which is moveable, or by a single 

 one resembling a hook or claw that is always moveable. The mouth is com- 

 posed of a labrum, 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, where there are four, by the same joint of the first pair 

 of feet, and of a ligula consisting of one or two pieces. 



FAMILY I. 



ARANEIDES. 



THIS family is composed of the genus ARANEA, Lin., or the Spiders. They 

 have palpi resembling little feet, without a forceps at the end, terminated at 

 most by a little hook. Their frontal chelicera; (the mandibles of authors) arc 

 terminated by a moveable hook, flexed inferiorly, underneath which, and near 

 its extremity, which is always pointed, is a little opening, that allows a passage 

 to a venomous fluid contained in a gland of the preceding joint. There are 

 never more than two jaws. The thorax usually marked with a depression in 

 the form of a V, indicating the space occupied by the head, consists of a single 

 segment, posteriorly to which, by means of a short pedicle, is suspended a 



