H Y A 



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H Y D 



HY' ALINE, (from hyalus, Lat. va\os, 

 Gr.) Transparent. 



HY'ALITE. (m\os, Gr.) The Hya- 

 lith of Werner ; quartz hyalin eon- 

 cretionne of Haiiy. A yellowish 

 or greyish variety of uncleavable 

 quartz or opal. It exhibits the 

 usual appearance of a concretion, 

 and differs but little from calcedony, 

 except in possessing a vitreous 

 lustre, and sometimes a loose tex- 

 ture. It is found in secondary trap 

 rocks; it occurs in grains, fila- 

 ments, and botryoidal masses. It 

 is infusible before the blow-pipe. 

 It is nearly all silica, its component 

 parts being silica 92-00, water 6'33. 

 Specific gravity from 2-4 to 2'11. 



HYBER'NACLE. | (hilernacula, Lat.) 1. 



HIBEB/NACLE. ) The winter dwell- 

 ing or residence of animals. 

 2. In botany that part of the plant 

 which defends the embryo from in- 

 juries arising from frost. 



HY'BODONT. (from /3o, Gr. and 

 dens, Lat.) A sub-family of sharks, 

 according to the arrangement of M. 

 Agassiz. They seem to have be- 

 gun with the coal formation, to 

 have continued throughout the 

 oolitic deposition, and to have 

 ceased at the beginning of the chalk 

 formation. The teeth of this sub- 

 family possess characters interme- 

 diate between the blunt crushing 

 teeth of cestracionts, and the sharp 

 cutting teeth of squaloids. 



HYB'ODUS. A genus of fishes that 

 prevailed throughout the oolitic 

 period. Not a single genus of all 

 that are found in the oolitic series 

 exist at the present time. 



HY'BRID. (vfipis, Gr. hylrida, Lat. 

 hydride, Fr.) Mongrel ; a term ap- 

 plied both to plants and animals, 

 when of a cross-breed. 



HTDA'TID. (va<?, Gr. hydatide, Fr.) 

 An order of internal worms. In 

 hydatids there has not been discov- 

 ered any vascular system. Hyda- 

 tids, so frequently found in the 

 liver and other parts of the body in 



mammalia, have been considered 

 by some as animals, consisting 

 merely of a stomach ; by others, as 

 a matrix, or womb, from something 

 like young hydatids being frequent- 

 ly found adhering to their inner 

 side. Hydatids immersed in warm 

 water, immediately after being ob- 

 tained from a living animal, are 

 observed to have a contractile 

 power, but they have no external 

 opening ; they are pellucid spheri- 

 cal bodies, of different sizes and 

 kinds. Each consists of two coats, 

 the inner of which is extremely 

 delicate. They do not possess any 

 visible blood-vessels, though the 

 sac containing them has abundance 

 of vessels, nerves, &c., derived from 

 those of the organ with which it is 

 connected. Hydatids ought not to 

 be confounded with watery vesicles, 

 connected occasionally with the 

 kidney, &c., which are not enclosed 

 in cysts, have no small hydatids 

 adhering to their inner surface, and 

 want contractility. There are many 

 genera. 



HYDNOPHO'RA. The name given by 

 M. Fischer to a genus of stony 

 polypifers, fixed, aud incrusting 

 other bodies ; either forming a sub- 

 globose, gibbons, or located mass, 

 or spread in subfoliaceous lobes ; 

 the upper surface is set with small 

 stars raised in pyramids. The stars 

 project and are conical ; the central 

 axis is solid, simple, or dilated, 

 surrounded by radiating adhering 

 lamellaa. Many species, both re- 

 cent and fossil, have been described. 

 Lamarck formed the genus monti- 

 cularia for their reception. 



HY'DBATE. (from vdwp, water, Gr.) 

 A chemical compound in definite 

 proportions of a solid body with 

 water, still retaining a solid form. 

 It must, however, be borne in mind 

 that when water in combination 

 with other bodies contributes (as 

 in crystailized bodies) to their reg- 

 ular form and transparency, it is 



