ARC 



[33 ] 



ARE 



Cuvier, the arachnidans compose 

 the second class of articulated 

 animals provided with moveable 

 feet. They have no wings, and do 

 not undergo any metamorphosis, 

 merely casting their skin. The 

 majority of the arachnidans feed 

 on insects; some are parasitical, 

 living on vertebrated animals ; 

 others are found in flour, in cheese, 

 and on vegetables. Cuvier has 

 divided the arachnidans into two 

 orders, Pulmoname and Trachearise ; 

 the former he subdivided into two 

 families, Araneides and Pedipalpi ; 

 the latter into three families, 

 Pseudo-Scorpiones, Pycnogonides, 

 and Holetra. 



AEA'CHNOID. 



AEACHNOI'DES. 



1. A cobweb-like membrane, form- 

 ing one of the tunics or coats of 

 the brain. 



2. One of the tunics, or coats, of 

 the eye. 



3. A species of fossil madrepore. 

 AEB'OEEOTJS. (aboreus, Lat.) 



1. Belonging to trees, resembling 

 trees. 



2. A term used to distinguish such 

 mosses, or funguses, as grow upon 

 trees, from those that grow on the 

 ground. 



AEB'OEESCENCE. (from arloresco, Lat.) 

 The likeness of a tree, frequently 

 observed in crystallizations and in 

 mineral productions. 



AEG or A CIECLE. An arc of a circle 

 is any part of its circumference; 

 and the chord, or subtense of an 

 arc, is a straight line joining the 

 two extremities of that arc. 



A'ECA. A transverse inequilateral 

 shell: the beaks distinct; the 

 hinge with many teeth disposed in 

 a straight line. These are marine 

 shells. Lamarck particularizes 

 seven species. Pound recent and 

 fossil. 



AECA'CEA. A genus of shells dis- 

 tinguished by having numerous 

 small penetrating teeth disposed on 



both valves in a straight or bent 

 line. 



AECA'CEA. A family of bivalve con- 

 chifera, according to Lamarck, 

 consisting of shells provided with 

 a linear series of teeth on the 

 hinge. In this family Lamarck 

 places the genera Area, Cucullcea, 

 Pectunculus, and Nucula; to which 

 may be added Crenella (Brown), 

 Solenetta (Sowerby), Myopora 

 (Lea), Limopsis (Sassi), Byssoarca 

 (Swainson), andMacroden (Lycett). 

 Lycett. 



A'ECTIC. | (from M/J/CTO?, ursus; 



A'ECTICK. j arctique, Fr. artico It.) 

 Northern ; lying under the arctos, 

 or bear. 



A'ECTIC CIECLE. One of the lesser 

 circles of the sphere, twenty-three 

 degrees and twenty-eight minutes 

 from the north pole. The circle at 

 which the northern frigid zone 

 begins. This and its opposite, the 

 antarctic, are called the two polar 

 circles. 



A'BCTTAPUEE. The curvature of an 

 arch. 



AEENA'CEOUS. (arenaceus, Lat.) 



1. Sandy; having the properties, 

 or appearance, of sand. 



2. Growing in sand, a term applied 

 to certain plants which are called 

 arenaceous. " The surface of the 

 bank is covered with various arena- 

 ceous plants." 



A.EENA'CEOTTS QTJAETZ. Sand. There 

 are varieties of sand which are of 

 a pure white, or nearly so, as some 

 of the sands of Alum Bay in the 

 Isle of Wight, and which appear 

 to have resulted from the destruc- 

 tion of quartz. 



AEEN'DALITE. The name given by 

 Karsten to the mineral more com- 

 monly known as Epidote. For 

 description, see Epidote. 



AEENILI'TIC. Resembling sandstone; 

 having the quality of sandstone; 

 composed of sandstone. 



AEEO'METEE. (from apaio<s and ^erpeuj, 

 Gr. areometre, Fr.) An instrument 



