MAR 



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nipple, and adhere to it till they attain 

 the size of a mouse, which does not take 

 place till they are fifty days old, at which 

 period they begin to see. The discovery 

 of marsupials, both in tb.3 secondary and 

 tertiary formations, shows that, so far 

 from being of more recent introduction 

 than other orders of Mammalia, this 

 order is in reality the first and most 

 ancient condition, xinder which animals 

 of this class appeared upon our pla- 

 net. 



MA/RSUPITE. (from marsupium, a purse, 

 Lat.) The name given by Dr. Mantell, 

 from their resemblance to a purse, to a 

 genus of Crino'idea found in the chalk. A 

 specimen of one species, named by him 

 Marsupites Milleri, found near Brighton, 

 is beautifully figured in his Geology of 

 the South-East of England, and in his 

 Wonders of Geology. The following de- 

 scription of the marsupite I have ex- 

 tracted from the. above two works of Dr. 

 Mantell's : " The marsupite was a mol- 

 luscous animal, of a sub-ovate form, hav- 

 ing the mouth in the centre, and sur- 

 rounded by arms, or tentacula. The 

 skeleton was composed of crustaceous, 

 hexagonal plates ; the arms, which are 

 subdivided into numerous branches, of 

 ossicula, or little bones : the whole was 

 invested with a muscular tissue, or mem- 

 brane. When floating, the creature could 

 spread out its tentacula like a net, and by 

 closing them, seize its prey, and convey 

 it to its mouth. The fossil remains of 

 this zoophyte, of which one species only 

 is known, have hitherto been found in 

 the upper chalk of Sussex, Wiltshire, and 

 Yorkshire only. The name of ' cluster- 

 stones, 1 given to them by the quarry- 

 men of Sussex, conveys an idea of their 

 general appearance. They may, how- 

 ever, so far as their body is concerned, be 

 compared to the fruit of the pine. The 

 body is orbicular, contained in a pelvis 

 composed of sixteen convex, radiated, 

 angular, crustaceous plates." 



MARSU'PIUM. The name given to a dark- 

 coloured membrane situated in the vitre- 

 ous humour of the eye of birds. The 

 use of the marsupium is not ascertained, 

 but it is present in almost every bird hav- 

 ing extensive powers of vision. 



MA'SCAGNINE. A native sulphate of am- 

 monia, found, by Mr. Mascagni, near the 

 warm spring of Sasso, in Tuscany, and 

 named after its discoverer. It has also 

 been called Sassolin, from the place near 

 which it was found. 



MA'SSETER. (from /^ao-ffaojucu, Gr. to 

 chew.) A muscle connected with the 

 under jaw of insects, and which assists in 

 masticating. 



MA'STODON. (from naorbq, a breast, and 



6ou , a tooth, Gr.) For a full descrip- 

 tion of the Mastodon, see Mammoth. 



MA'STOID. (from juaoro^, the breast, and 

 ioc, likeness, Gr.) Shaped like the 

 breast, or like a nipple. Applied to 

 some prominences of bones ; to a fora- 

 men ; to a muscle ; and to cells in the 

 ear. 



MA'TRIX. (matrix, Lat. matrices, pi.) 

 The earthy or stony matter in which a 

 fossil is imbedded. 



MAXI'LLA. (maxilla, Lat.) The jaw. 

 The lower jaws of insects are called 

 maxillae ; they are placed behind the 

 mandibles, and between is situated the 

 labium, or lower lip. The maxillae are 

 employed principally for holding the sub- 

 stanCes on which the grinding apparatus 

 of the mandible is exerted. 



MA'XILLARY. Belonging to the maxilla, or 

 attached to it. 



MAW. (magen, Germ*) The craw of 

 fowls ; the stomach of brutes. 



MEANDRI'NA. Brain-stone ; brain-coral. 

 Madrepores in which the laminae assume 

 a meandering direction are called mean- 

 drinse. Meandrinse are large hemis- 

 pherical corals, having their surface co- 

 vered with serpentine ridges and depres- 

 sions, resembling the convolutions of the 

 cerebrum, or brain, from which circum- 

 stance they have been called brain-stone. 

 A very fine specimen, four feet in -cir- 

 cumference, may be seen in the British 

 Museum, presented by the late Dr. Jar- 

 vis, of Margate. 



MEA'TUS. (meatus, Lat. from meo, to 

 flow.) A passage, as that leading to the 

 ear, called the meatus auditorius, &c. 



MECHA'NICAL ORIGIN. A term used, says 

 Mr. Lyell, to distinguish rocks of sand, 

 pebbles, or fragments, from those of 

 chemical origin ; or such rocks as are of a 

 uniform crystalline texture. 



MEDU'LLA. (medulla, the marrow, Lat) 



1. In botany, the pith of plants. 



2. The marrow in the cavities of bones. 

 MEDU'LLARY. (medullaris, Lat.) 



1. Relating to the brain, or to the marrow. 

 The medullary substance composes the 

 greater part of the brain, spinal marrow, 

 and nerves. 



2. In botany, relating to the pith of 

 plants . 



MEDU'LLIN. A name given by Dr. John to 

 the porous pith of the sun-flower. 



MEDU'SA. A genus of marine molluscous 

 animals belonging to the class Acalepha. 

 The medusa approach nearly to the fluid 

 state, appearing like a soft and trans- 

 parent jelly, which by spontaneous de- 

 composition after death, or by the appli- 

 cation of heat, is resolved almost into a 

 limpid watery fluid. The usual form of 

 a medusa is that of a hemisphere, with a 



