G Y R 



HAM 



and the beds of marl are not -so uu- 

 merous ; it is chiefly in this mass that 

 fossil fish are found. The uppermost 

 mass is the most remarkable and impor- 

 tant of all ; it is in some parts more than 

 seventy feet thick ; there are but few beds 

 of marl in it ; the lower strata of gypsum 

 in this mass have a columnar structure. 

 In this upper mass of gypsum the skele- 

 tons and scattered bones of birds and 

 unknown quadrupeds are discovered. 

 Remains of turtles and crocodiles have 

 been also found in the same strata." For 

 a further and more interesting detail, 

 see Bakewell's Introduction to Geology. 

 GY'RODUS. A fossil fish of the family of 



Pycnodonts, or thick-toothed fishes, found 

 in the oolite of Durrheim, in Baden. 

 GYRO'GONITE. (from yvpog, curvus, and 

 ysvog, genus.) Petrified seed-vessels of 

 the Chara hispida. These bodies are 

 found in fresh-water deposits, and were, 

 not very long since, supposed to be mi- 

 croscopic shells, indeed they are thus 

 described by Parkinson, who concludes 

 his notice of them by stating, " Lamarck 

 observes, that it has the form of a very 

 small seed of some species of lucern ; 

 and hesitating at determining it to be 

 really a multilocular shell, only assumes 

 it as such for the present." 



H 



HA'BITAT. Habitation ; place of abode. 



HA'BITUDE. (habitude, lint, habitude, Fr. 

 abitudine, It.) Customary manner or 

 mode of life. 



HADE. A term used by miners; to dip. 



HA'DING. The dip from the perpendicular 

 line of descent ; the dipping of a vein. 



HJE'MATITE. (i/tarir;c., Gr. haematites 

 lapis, Lat.) Blood-stone, an iron ore ; 

 it occurs in masses of various shapes, 

 both globular and stalactitic. 



HAJLIO'TIS. (from aXor, mare, and OJTOQ, 

 auris, Gr.) The sea-ear. A shell, both 

 fossil and recent, obtaining its name from 

 the excessive amplitude of its aperture, 

 and the flatness and smallness of its 

 spire, whence it has been likened to an 

 ear. The shells of this genus are said, 

 by Mr. Parkinson, to be among the 

 rarest fossils. The recent shells are 

 littoral, and found adhering to rocks ; 

 they are very beautiful, and are remarka- 

 ble 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 communication 

 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 Rev. W. Kirby, " a very 

 large specimen, in which there are traces 

 of eighteen apertures, and all but six are 

 stopped up." The soft parts of the in- 

 habitant of this shell are eaten in some 

 places, and are esteemed as being deli- 

 cious. 



HA'LOIDE. (from a\f , salt, and ei^oc, Gr. 

 form or appearance.) An order of 

 earthy and metalliferous minerals ; taste- 

 less ; specific gravity from 2-2 to 3' 3. 



HALTE'RES. (aXriJpff, Gr. halteres, Lat) 

 The poisers, so named from their sup- 

 posed use in balancing the body, or ad- 

 justing with exactness the centre of gra- 

 vity when the insect is flying. In those 

 insects which compose the order Diptera, 

 we meet with two organs, consisting of 

 cylindrical filaments, terminated in a 

 clubbed extremity ; one arising from 

 each side of the thorax, in the situation 

 in which the second pair of wings origi- 

 nate in those insects that have four wings ; 

 these are called halteres. Whatever 

 may be their real utility, they may still 

 be regarded as rudiments of a second 

 pair of wings. 



HA'MITE. (from hamus, Lat. a hook.) Agenus 

 of fossil multilocular hook-formed shells. 

 Parkinson states that the hamite has 

 no evident siphunculus, but this is a mis- 

 take ; the siphuncle of the hamite, like 

 that of the ammonite, is placed on the 

 back, or outer margin of the shell, and in 

 some species this marginal siphuncle has 

 a keel-shaped pipe raised over it. The ex- 

 ternal shell is fortified by transverse folds 

 or ribs, which serve to strengthen both 

 the outer and the air chambers. The 

 hamite is sometimes found of large size, 

 more especially that species known as 

 Karaites grandis ; some of them are of 

 the diameter of a man's wrist. Nine spe- 

 cies are stated to have been discovered 

 in the gault or Speeton clay immediately 

 below the chalk in Yorkshire. Dr. Man- 

 tell gives the following as found in Sus- 

 sex: In the chalk one species, Hamites 

 armatus. In the chalk mark five species, 

 H. armatus, H. plicatilis, H. alternatus, 

 H. ejlipticus, H. attenuatus. In the gait six 



