H E U 



[215 J 



H I 



tral shells. Synonymous with 

 Heterocrital. 



HETJ'LANDITE. Hemi-prismatic zeo- 

 lite, or foliated zeolite. A min- 

 eral thus named after Heuland. 

 It occurs in drusy cavities, in 

 secondary trap rocks, in the Hartz 

 mountains, in Ireland, and in 

 Scotland. It is of different 

 colours, white, grey, brown, and 

 red. Its constituent parts are 

 silica 59, alumina 16*87, potash 8, 

 (or, according to others, lime 9,) 

 water 16 '5. Specific gravity 2 '20. 

 Hardness 3*5 to 4. It commonly 

 is found crystallised in right oblique 

 angled prisms (two of its opposed 

 lateral planes being longer than the 

 other two) generally modified on 

 the angles and one lateral edge. It 

 also occurs massive, frequently in a 

 globular form, and is easily frangible. 



HE'XAGON. (hexagone, Pr. esdgono, 

 It. egd^wvos, Gr. from ef six, 

 and 7wi//o, angle.) A figure of six 

 sides or angles ; the most capacious 

 of all the figures that can be added 

 to each other without any interstice. 

 The cells of the honeycomb are 

 hexagons. 



HE'XAGYN. (from e, six, and ^vvrj 

 Gr. a woman.) A plant having six 

 pistils. 



HEXAGT'ETAN". Having six pistils. 



HEXAHE'DRAL. Having six sides 

 equal to one another ; cubal. 



HEXAHE'DRON. (from e and efya, Gr. 

 hexaedre, Fr. esaedra, It.) A cube; 

 a solid body having six equal faces. 



HEXA'NDEB. (from e', six, and avrjp, 

 Gr. a man.) As plants which have 

 six pistils are denominated hexa- 

 gyns, so those with six stamens are 

 termed hexanders. 



HEX'ANDRIAN. Having six stamens ; 

 belonging to the sixth class in 

 Linnaeus' s sexual method. 



HEXA'NGULAR. from eg and angulus.} 

 Having six angles. 



HE'XAPED. } e|fo7ro'&7<?, (from ejf and 



HE'XAPOD. ) Trofo, Gr.) An animal 

 with six feet. 



HEXAPE'TALOUS. (from ef, six, and 

 7reTa\ov, Gr. a leaf.) A plant 

 having six petals; a corolla con- 

 sisting of six petals. 



HEXAPHY'LLOTJS. (from ejf and 0v\Xoi/, 

 Gr.) Six -leaved. 



HIG'HTEA. The name assigned by 

 Mr. Bowerbank to a genus of fossil 

 fruits found in the London clay, 

 and thus named in honour of an 

 able botanist, John Hight, Esq. 

 The following is Mr. Bowerbank' s 

 description, "pericarp one celled, 

 valveless. Placenta central, usually 

 five, rarely four, or six angled, ob- 

 conical and very large, with one or 

 more seeds attached to each angle. 

 Seeds and placenta enveloped in a 

 mass of downy or filamentous 

 structure, which fills up the whole 

 of the remaining space within the 

 pericarp. Seed about two or three 

 times its own diameter in length, 

 angular and somewhat curved. 

 Testa reticulated. Ten species 

 have been distinguished by Mr. 

 Bowerbank, and are beautifully 

 figured in his " History of the 

 Fossil Pruits of the London Clay." 



HI'LTTM. (Mum, Lat.) In botany, 

 the small mark on seeds showing 

 the spot where they were joined to 

 the fruit. 



HINGE. In conchology, the point by 

 which bivalve shells are united : it 

 is formed by the teeth of the one 

 valve inserting themselves between 

 those of the other, or by the teeth 

 of one valve fitting into the cavities 

 or sockets of the opposite valve. 



It is on the peculiar construction 

 of the hinge that the generic 

 character of bivalve shells is mainly 

 founded, in connection with the 

 general form of the shell. Some 

 hinges have no visible teeth, and 

 are termed inarticulate ; hinges with 

 few teeth are termed articulate; 

 those having many teeth are called 

 multiarticulale. 



HINNI'TES. A genus of eared ir- 

 regular bivalves, separated from 



