H E T 



HIP 



turn in a contrary direction to the usual 

 way ; sinistral. In shells, the axis of 

 revolution is termed the columella, and 

 the turns of the spiral are denominated 

 whorls. In consequence of the situation 

 of the heart and great blood-vessels rela- 

 tively to the shell, the left side of the 

 mantle is more active than the right side, 

 so that the lateral turns are made in the 

 contrary direction. Sometimes, in con- 

 sequence of the heart being placed on the 

 right side the turns of the spiral are made 

 to the left : this left-handed convolution 

 seldom occurs among the shells of land or 

 fresh -water mollusca. 



HETERO'STROPHE. (trtpoarpo^a, Gr. ex 

 *Tpo et crr)0o^j}.) A term applied to 

 reversed shells, or shells whose spires 

 turn in a contrary direction to the usual 

 way ; sinistral shells. Synonymous with 

 Heterocrital. 



HEU'LANDITE. Hemi-prismatic zeolite or 

 foliated zeolite. The Stilbite of Haiiy. A 

 mineral, 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 consti- 

 tuent parts are silica 59, alumina 16'87, 

 potash 8, (or, according to others, lime 

 9,) water 16'5. 



HE'XAGON. (Jiexagone, Fr. esayono, It.) 

 fdyovo, Gr. from t'4, six, and ywvia, 

 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. 



HEXA'GONAL. Six-sided. 



HE'XAGYN. (from ?, rx, and yvvfi, Gr. 

 a woman.) A plant h- nng six pistils. 



HEXAGY'NIAN. Having six pistils. 



HEXAHE'DRAL. Having six sides equal to 

 one another ; cubi-i.!. 



HEXAHE'DRON. (from t and tdpa, Gr. 

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

 solid body having six equal faces. 



HEXA'NDER. (from !, six, and avrjp, Gr. 

 a man.) As plants which have six pistils 

 are denominated hexagyns, so those with 

 six stamens are termed hexanders. 



HEX'ANDRIAN. Having six stamens ; be- 

 longing to the sixth class in Linnaeus' s 

 sexual method. 



HEXA'NGULAR. (from t and angulus.) 

 Having six angles. 



HE'XAPED. ) (iZo-jrodrjg, from f and TTQVQ, 



HE'XAPOD. ) Gr.) An animal with six 

 feet. 



HEXAPE'TALOUS. (from t, six, and TrlraXov, 

 Gr. a leaf.) A plant having six petals ; 

 a corolla consisting of six petals. 



HEXAPHY'LLOUS. (from t'f and <pv\\ov, 

 Gr.) Six- leaved. 



HI'LUM. (hilum, 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 them- 

 selves 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 con- 

 nection 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 multiarticulate. 



HIPPOPO'TAMUS. (iTTTroTrorctjuoc, Gr. hip- 

 popotame, Fr. ippopotamo, It.) The 

 hippopotamus, or river-horse, belongs to 

 the order Pachydermata, or thick-skinned 

 animals, class Mammalia. This genus of 

 quadrupeds has four fore-teeth in the 

 upper jaw, disposed in pairs at a distance 

 from each other ; and four prominent 

 fore-teeth in the under jaw, the inter- 

 mediate ones being longest. There are 

 two tusks in each jaw, those of the under 

 being long, and obliquely truncated ; in 

 both they stand solitary, and are recur- 

 vated. The feet are hoofed on the edges. 

 The head is of an enormous size, and the 

 mouth vastly wide. The ears are small 

 and pointed. The eyes arid nostrils are 

 small. The body is naked. The tail is 

 about a foot long, taper, compressed, and 

 naked. The legs are short and thick ; 

 the belly reaching to the ground. One 

 species only is known, the hippopotamus 

 amphibius, confined to the rivers of 

 Africa. 



Fossil bones and teeth of the hippopo- 

 tamus are abundantly found in England, 

 France, Germany, and Italy ; several ex- 

 tinct species have been determined by 

 Cuvier. The head of a hippopotamus 

 was found in Lancashire, under the peat ; 

 bones and teeth are found in large quan- 

 tities in the Val d'Arno, in Italy, and in 

 alluvial deposites in the neighbourhood of 

 Rome. 



HI'PPOPUS. (from 'ITTTTOQ, a horse, and 

 TTO ug, a foot. ) A subtransverse, equivalve, 

 inequilateral shell ; lunule closed with 

 crenulated edges ; the hinge formed of 

 two long compressed entering teeth in one 

 valve and three in the other ; the cres- 

 cent closed. Parkinson states that he 

 does not know of any fossil shells of this 

 genus having been found, but Sowerby 

 mentions fossil species. 



HIPPOTHE'RIUM. (from ITTTTOC, and $r]- 

 plov, Gr.) An extinct animal, allied to 

 the horse, belonging to the miocene 

 period. 



