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of the family of Pycnodonts, or 

 thick-toothed fishes, found in the 

 oolite of Durrheim, in Baden. 

 GYRO'GONITE. (from ryv/>oe, curvus, 

 and 761/09, genus.) Petrified seed- 

 vessels of the Chara. These bodies 

 are found in fresh- water deposits, 

 and were, not very long since, sup- 

 posed to be microscopic shells, in- 



deed they are thus described by 

 Parkinson, who concludes his no- 

 tice of them by stating, " Lamarck 

 observes, that it has the form of a 

 very small seed of some species of 

 lucern ; and hesitating at determin- 

 ing it to be really a multilocular 

 shell, only assumes it as such for 

 the present." See Chara. 



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HACKL'Y. A term used in mineralogy 

 to designate a fracture with a 

 peculiarly uneven surface, similar 

 for instance to that of pure copper. 

 This term, says Mr. Allan, relates 

 to a fracture which is peculiar to 

 the malleable metals. 



HADE. A term used by miners ; to 

 dip. 



HADE. | The dip from the perpen- 



HA'DING. j dicular line of descent; 

 the angle of inclination of a vein. 



HEMATITE. | (at/LLaThps, Gr. hama- 



HE'MATITE. ) tites lapis, Lat.) 

 Blood-stone, an iron ore ; it occurs 

 in masses of various shapes, both 

 globular and stalactitic. 



HALF-MOON SHAPED. A figure for- 

 med by the portion of a circle cut 

 off by the segment of a larger 

 circle. 



HALINI'DA, An order, the lowest, of 

 the class Poriphera, and thus de- 

 nominated from the composition of 

 the skeleton, which consists of 

 minute silicious crystalline spicula. 



HALIO'TIS. (from a\a, mare, and WTO?, 

 amis, Gr.) The sea-ear. A shell, 

 both fossil and recent, obtain- 

 ing its name from the exces- 

 sive amplitude of its aperture, 

 and the flatness of its spire, 

 whence it has been likened to an 

 ear. The shells of this genus are 



said to be among the rarest fossils. 

 The recent shells are littoral, and 

 found adhering to roeks ; they are 

 very beautiful, and are remarkable 

 for the pearly irridescence of the 

 inner surface, and for the shell 

 being perforated along the side of 

 the columella by a series of holes ; 

 they are amongst the most highly 

 ornamented of all the gasteropoda. 

 The sea-ears protect their open 

 side by fixing themselves to the 

 rocks, and preserve a communica- 

 tion with the atmosphere, or water, 

 without elevating their shells, by 

 means of a line of apertures, under 

 the thickest margin, near the apex : 

 these apertures begin, when the 

 animal is young, near the spire, 

 and as it grows it stops up one 

 and opens another, as its occasions 

 require. " I have," says the Kev. 

 "W. Kirby, " a very large specimen, 

 in which there are traces of eight- 

 een apertures, and all but six are 

 stopped up." The soft parts of 

 the inhabitant of this shell are 

 eaten in some places, and are es- 

 teemed delicious. 



HA'LITHEBITJM. The name assigned 

 to an extinct genus of mammalia 

 of the Eocene period. 



HA'LOIDE. (from \9, salt, and e?o?, 

 Gr. form or appearance.) An order 

 of earthy and metalliferous mine- 



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