410 THE MOUNTAIN. 



curious and extraordinary animals will be finally explored, 

 and rendered accessible to all students of nature. The 

 mountain has but few crustaceans. They are, however, of 

 great interest, and their story will hereafter be told.* 



CLASS IILARACHNIDA. 



" This class includes the various articulate forms known 

 as spiders, mites, and scorpions, the characters of which 

 place them between the Crustacea and Insecta. In general, 

 the head is not distinct from the thorax, but intimately con- 

 nected with it, forming a large segment named the cephalo 

 thorax, which is followed by the abdomen, and this is either 

 distinct or united in a single piece with the former. These 

 animals are not subject to a perfect metamorphosis, but they 

 have, in some cases, a partial one. They have neither wings, 

 antennae, nor upper lip ; feet, eight, affixed to the sternum ; 

 mouth provided with a pair of mandibles or chelicera ; eyes 

 simple, two to eight, position and number much used as 

 generic characters. Most of the Arachnida feed upon fresh 

 animal food, as insects, which they take alive either in nets, 

 or by running or suddenly leaping upon them. Some are 

 parasitic, others live in meat, cheese, figs, and flour. They 

 are mostly oviparous, and, like the Crustacea, moult or 

 change their integument from time to time."f 



The class Arachnida is divided into two orders, Pulmo- 

 narise and Trachearioa.J The first is characterized as hav- 

 ing "pulmonary sacks, and six or eight simple eyes." The 

 second respire by " tracheae, have no organs of circulation, 

 or incomplete ones ; the tracheae divide into branches, which, 

 unlike the insect, do not run parallel to each other, the 

 whole body receiving air from various points by stigmata ; 

 ocelli four at most." 



* Heck, pp. 118, 119, vol. ii. 



f According to Heck, the class is divisible into three sections, 

 Aporobranchia, Trachearia, and Pulmonaria. 



The ancient, order of fossil crustaceans, called Trilobites, belong 

 here. Many localities of this interesting fossil are found near the 

 eastern base of the Alleghany Mountain. 



