PUT 



[374] 



P Y K 



PFTA'MEN. (putamen, Lat. a shell of 

 a nut.) In botany, another name 

 for the endocarp, stone, or shell of 

 certain fruits. 



PJCNODO'NTID^. According to some 

 naturalists, a family of extinct 

 fishes of the order Ganoidea Rhom- 

 bifera. This family comprises 

 many genera, namely, Pycnodus, 

 Gyrodus, Phyllodus, &c., &c. 



PY'CITODONTS. (from TTVKVO-S, thick, 

 and 080 v?, a tooth, Gr.) Thick- 

 toothed fishes. An extinct family 

 of fishes which prevailed exten- 

 sively during the middle ages of 

 geological history. Their leading 

 character consists in a peculiar 

 armature of all parts of the mouth 

 with a pavement of thick, round, 

 and flat teeth, the remains of which, 

 under the name of bufonites, occur 

 most abundantly throughout the 

 oolite formation. 



PYCNO'DTJS TRIGONUS. A genus of 

 thick-toothed fishes, belonging to 

 the family of Pycnodonts. 



PY'CNITE. A mineral of a yellowish- 

 white colour, found principally at 

 Altenberg, in Saxony. 



PYBA'LLOLITE. (from Trvp, fire, aXXos, 

 and X/009, a stone, Gr., in allusion 

 to its change of colour when ex- 

 posed to the action of fire.) An 

 earthy mineral discovered by Nor- 

 denskiold in the lime quarries, at 

 Pargas, in Finland. It is a tri- 

 silicate of magnesia mixed with 

 hydrate of the same. Its analysis, 

 according to Nordenskiold, gives 

 silica 56-62, magnesia 23-28, alu- 

 mina 3'41, lime 5*56, proxide of 

 iron 0'99, protoxide of manganese 

 0'99, water 3'58. Specific gravity, 

 2'55; hardness, 3*5. It occurs mas- 

 sive, and crystallized in flat rhombic 

 prisms, much resembling those of 

 tremolite, and is divisible parallel 

 to the planes of a rhombic prism : 

 the prisms are generally above an 

 inch in length, have occasionally 

 a greenish tinge, but by exposure 

 become of a pale yellow, and are 



then soft and friable. Phillips. 



PY'RAMTD. (w^o/us, Gr., from irvp, 

 fire ; pyr amide, Fr. pyr amide, It.) 

 The name given to a certain figure, 

 from its resembling the shape of 

 flame. A solid figure, whose base 

 is a polygon, and whose sides are 

 plain triangles, their several points 

 meeting in one. In mineralogy, 

 a pyramid is formed by the meeting 

 of three or more planes at a point, 

 which is termed the apex, each 

 plane being bounded by edges ; 

 considered separately, a pyramid 

 is supposed to have a base, which 

 is the case in regard to the tetra- 

 hedron; but in respect of such 

 other forms, it is only imaginary, 

 as in the instance of the octahedron, 

 which is often termed a double 

 four-sided pyramid; and also the 

 dodecahedron with triangular faces, 

 which is frequently denominated 

 a double-sided pyramid. 



PYBAMIDE'LLA. A genus of marine 

 univalves, belonging to the family 

 Plicacea. It is found on coral reefs, 

 sands, and sandy mud, at depths 

 varying to twelve fathoms. The 

 pyramidella is a turriculated uni- 

 valve ; opening entire and semi- 

 oval; columella projecting, with 

 three transverse folds, and perfo- 

 rated at its end. 



PY'RENAITE. | A greyish -black dode- 



PY'BENEITE. ) cahedral, opaque va- 

 riety of dodecahedral garnet. It 

 consists of silica 43, alumina 16, 

 lime 20, oxide of iron 16, water 4. 

 It is found in the Trench Pyrenees, 

 from which circumstance it has 

 obtained its name, in limestone. 



PY'RGOM. (Called also Fassaite.) An 

 earthy mineral of a dingy green 

 colour ; a variety of augite. 



PYRI'TES. (irupiTijs, Gr. pyrites, Lat. 

 pyrite, Fr.) Sulphuret of iron. 

 The fersulfure of Haiiy, who has 

 described sixteen modifications of 

 the primitive form of its crystals. 

 The colour of pyrites is usually 

 bronze yellow, passing to brass 



