434 



tractile skin of the mollusca, 

 which covers the viscera and a 

 great part of the body like a cloak. 



Marl, earth principally composed of 

 decayed shells and corals, a mix- 

 ture of clay and lime. 



Marsupial animals found in the 

 oolite, 674. 



MarsupiaMia (Latin, marsvpium, a 

 purse), an order of the Mammalia 

 having a tegumentary pouch, in 

 which the embryo is received 

 after birth, and protected during 

 the completion of its development. 



Alassive rocks, 646. 



MasticaHion, 334 ; confined to the 

 mammalia, 341. 



Mas'todon (Gr. /uaorog, a teat; 

 ooov, a tooth), a genus of extinct 

 quadrupeds allied to the elephant, 

 but having the grinders covered 

 with conical protuberances like 

 teats, 687. 



Matrix, the organ in which the 

 embryo is developed, 475. 



Matter and mind, to be contemplated 

 together, 29. 



Maxilla (Lat. maxilla, a jaw-bone), 

 in entomology restricted to the 

 inferior pair of jaws. 



MeMian, having reference to the 

 middle line of the body. 



Medulla oblongaHa, the oblong me- 

 dullary column at the base of the 

 brain, from which the spinal 

 chord or marrow is continued, 89. 



Medu v sa, development of the, 527 

 529. 



Medu'sa, a class of soft radiated ani- 

 mals, or acalephs, so called because 

 their organs of motion and pre- 

 hension are spread out like the 

 snaky hair of the fabulous Medusa. 



Megalosau'rus, an extinct reptile, 673. 



Mergan'ser, an aquatic bird allied 

 to the goose, 593. 



Memory, 188. 



Mes entery (Gr. /uecroc, intermediate ; 

 and tvTtpo$, entrail), the mem- 



brane which forms the medium 

 of connection between the small 

 intestines and the abdomen. 



MesothoVax (Gr. yuetrof, middle; 

 9opa, the chest), the intermediate 

 of the three segments which form 

 the thorax in insects. 



Metacar'pus, the wrist, 276. 



Metamor'phic rocks, 647. 



Metamo/phoses (Gr. ^isra^op^wo-ig, 

 change of form), of animals, 548 ; 

 of vegetables, 549. 



Metatar'sus, one division of the 

 bones of the foot, 267. 



MetathoVax (Gr. JJ.STO, after ; 6opa%, 

 the chest), the hindmost of the 

 three segments which compose 

 the thorax of an insect. 



Migration little prevalent among the 

 mammalia, 594. 



Mil'lepeds (Lat. milk, a thousand ; 

 pes, a foot), animals with many- 

 feet, as the wood-louse. 



Millepores x (Lat. mille, a thousand ; 

 Gr. Tropoc, a minute hole"), a genus 

 of lithophytes, having their sur- 

 face penetrated by numerous little 

 holes. 



Miocene x (Gr. fieiov, less ; ican'Of, 

 recent), the stage of the tertiary 

 epoch in which a minority of 

 the fossil shells are of recent 

 species, 650. 



Modern age, the reign of man, 658, 

 684686. 



Mo'lar (Lat. molaris, grinding) teeth, 

 341. 



Molecules v (of moles, a mass), mi- 

 croscopic particles. 



Mollusca (Lat. mollis, soft), or Mol'- 

 lusks, a primary division of the 

 animal kingdom, xxii. 



Mollusca, 70, 662 ; of the trias 

 period, 670; in the oolite, 673; 

 nervous system, 116; digestive 

 organs, 318 321; jaws, 336; 

 circulation, 368 ; respiration, 380, 

 405. 



Mon'ad (Gr. /tioi-rt'.;, unity), the 



