CLAVARIA 



CLAY 



288 



distribution are known. The fossil forms, which 



Clavagella lata, showing the cavity and fixed valve : 

 a, the fixed valve ; 6, the calcareous tube. 



are more numerous, were first discovered. They 

 do not occur below the Upper Chalk. 



Clavaria, a genus of Fungi, of the order 

 Hymenomycetes, family Clavariei, in which the 

 spore-bearing tissue is produced over all parts of 

 the surface. The species are numerous, some of 

 them simple and club-shaped, some branched. 

 C. botrytis, a species common in oak and beech 

 woods, especially in Germany, growing on the 

 ground, among moss, grass, heath, &c., is gathered 

 when young and used as food, having a very agree- 

 able sweetish taste. (Botrytis is also the name of 

 a genus of Ascomycete Fungi.) Other species of 

 Clavaria, notably C. flava, coralloides, aurea, and 

 fonnosa, are used in the same way. See FUNGI. 



Claverhou.se. See GRAHAM (JOHN). 



Clavichord, an obsolete instrument of the 

 same type as the Harpsichord (q.v. ) and Spinet 

 (q.v.). A Claviharp is a harp struck with Keys 

 like a piano. 



Clavicle, an important part of the pectoral 

 girdle of Vertebrates, perhaps most familiarly 

 known in the collar-bone of man and in the 

 merry-thought of birds. It is well developed in 

 those mammals in which the fore-leg or arm is used 

 very strongly and freely, but is poorly developed 

 or absent in many cases, as in Carnivores and 

 Ungulates. In most Hying birds it is strong, and 

 often fused to the breast-bone ; in the ostrich tribe 

 it is rudimentary or absent. It is not a prominent 

 bone in reptiles, being absent in snakes and croco- 

 diles, apparently continuous with the scapula in 

 tortoises, and in fact only well seen in the majority 

 of lizards. A ' clavicle ' is also to be seen in most 

 Amphibia, though its exact relations are much 

 disputed. A prominent part in the girdle of ordi- 

 nary bony fishes is also called the ' clavicle,' but it 

 is not certain that it corresponds to that of higher 

 vertebrates. Of the clavicle generally it may be 

 said that it is a paired bone superadded from the 

 *kin as an auxiliary to scapula and coracoid, 

 that its position is ventral and anterior to the 

 coracoid, and that it is often associated with an 

 interclavicle. See BIRD, BONE, SKELETON ; also 

 Huxley's Anatomy of the Vertebrate Animals, and 

 other works on Comparative Anatomy, such as 

 those of Gegenbaur and Wiedersheim (translated 

 by Professors Bell and Parker). There is a separ- 

 ate article on the human COLLAR-BONE (q.v.). 



Clavicor'nia* a name Hometirnes applied to 

 SCMTJI) trileH of beetles with club-shaped (clavate) 

 antenna*. They are included within the great 

 Pentamerous section of Coleoptera. burying 

 beetles illustrate the type. 



Clavije'ro, FRANCISCO XAVIER, Mexican hi*- 

 torian, horn at Vera Cruz in 1721, entered the 

 order of the Jesuits in 1748, and became a teacher 

 of philosophy. On the suppression of the JesuiUi 

 in 1767, he retired to Italy, where he died at 

 Bologna in 1787. He wrote in Italian a History of 

 Mexico (Eng. trans. 1787). 



Clavijo y Fayardo, JOSE (1730-1806), a 

 Spanish publicist, who had a duel with Beau- 

 marchais, and was made, with a character much 

 altered, the hero of Goethe's Clavigo. 



Claws, a term often applied to the chela; at the 

 t-inl of Arthropod limbs, but best restricted to the 

 epidermic tips found at the ends of the digito in 

 most reptiles, on the toes, and often on the thumb 

 and first finger of birds, but seen in perfection in 

 many mammals e.g. Carnivores, Insectivores, 

 Edentates. It is obviously impossible to draw any 

 sharp line between claws and Kails (q.v.). 



Clay(A.S. clwg ; of the same root as'clag,' 

 'claggy'), a term applied, in a vague way, to 

 those kinds of earth or soil which, when moist, 

 have a notable degree of tenacity and plasticity. 

 The clays are not easily distinguished as rock 

 species, but they all appear to owe their origin to 

 the decomposition of various rocks, and to consist 

 chiefly of a/luminic silicate, along with other in- 

 gredients, which vary in character with the nature 

 of the parent rock from the degradation of which 

 they are derived. Thus common clay is a mixture 

 of kaolin or China clay ( which is a hydrated clay ), 

 and the fine powder of some felspathic mineral, 

 which is anhydrous and not decomposed. Clays 

 vary much in plasticity all being more or less 

 plastic when moistened with water, and capable of 

 being moulded into any form. But while many 

 retain their shape when dried bv heat, others, 

 which in the damp state would ordinarily be called 

 clays, tend to fall to powder when all the water is 

 driven off. Clay is eaten by the Botocudos and 

 other savage tribes, as also in Georgia and the 

 Carolinas by negroes and 'poor whites.' The 

 plastic clays are used for many purposes, as for 

 making pottery of all kinds, bricks and tiles, 

 tobacco-pipes, firebricks, &c. The following are 

 the commoner varieties of clay and clay -rocks: 

 China clay or Kaolin (q.v.); Pipeclay (q.v.), very 

 like kaolin, but containing a larger percentage of 

 silica; potter's clay, not so pure as the preceding ; 

 sculptor's clay or modelling clay, a fine potter's 

 clay, sometimes mixed with fine sand ; plastilinu, 

 a potter's clay from Italy, supposed to be conipo-'<l 

 of oil, glycerine, rosin, and powdered clay, which, 

 as it does not shrink, need not be kept wet ; brick- 

 clay (see BRICK), an admixture of some clay and 

 sand with some ferruginous matter ; Fireclay 

 (q.v.), containing little or no lime, alkaline earth, 

 or iron (which act as fluxes), and hence infusible or 

 highly refractory; Male (q.v.), a laminated rlay- 

 rock ; clay-slate, an indurated cleaved clay-rock ; 

 Loam ( q.v. ), a non-plastic mixture of clay and sand ; 

 Marl (q.v.), a clay containing much calcareous 

 matter. Clay at the deepest sea- bottom is largely 

 of animal origin. See PETROGRAPHY. 



CLAY SOILS derive their character from the 

 aliiniinic silicate which they contain in a state of 

 mixture, as well as in chemical combination with 

 other substances. Some soils contain so large a 

 proportion of alumina as 35 per cent., but generally 

 the proportion is much smaller. The felspars 

 which chiefly yield the alumina of clay soils con- 

 tain also soda, potash, and lime, substances which 



