GLOSSARY. 493 



Maesipobranchii (Gr. viarsipos, a pouch ; bragchia, gill). The order of 

 Fishes comprising the Hag-tishes and Lamprej^s, with pouch-like gills. 



Maesupialia (Lat. marsupium, a pouch). An order of Mammals in which 

 the females mostly have an abdominal pouch in which the young are carried. 



Masticatory (Lat. mastico, I chew). Applied to parts adapted for chewing. 



Maxilla (Lat. jaws). The inferior pair or pairs of jaws in the Arthropoda 

 (Insects, Crustacea, &c). The upper jaw-bones of Vertebrates. 



Maxillipedes (Lat. maxillae, jaws ; pes, the foot). The limbs in Crustacea 

 and Myi'iapoda, which are converted into masticatory organs, and are com- 

 monly called "foot-jaws." 



Medl'LLA (Lat. marrow). Applied to the marrow of bones ; or to the spinal 

 cord, with or without the adjective "spinalis." 



Medusa. An order of Hydrozoa, commonly known as Jelly-fishes [Disco- 

 p>liora, or Acalephce), so called because of the resemblance of their tentacles 

 to the snaky hair of the Medusa. Many Medusae are now known to be 

 merely the gonophores of other Hydrozoa. 



Megalonyx (Gr. megas, great ; 07iux, nail). An extinct genus of Edentate 

 Mammals. 



Megalosatjeus (Gr. megas, great ; saura, lizard). A geniis of Deinosaurian 

 Reptiles. 



Megatheicium (Gr. megas, great ; therion, beast). An extinct genus of 

 Edentata. 



Meiiostomata (Gr. meron, thigh ; stoma, mouth). An order of Crustacea in 

 which the appendages which are placed round the mouth, and which offi- 

 ciate as jaws, have their free extremities developed into walking or pre- 

 hensile organs. 



Mesenteries (Gr. 7nesos, intermediate ; entermi, intestine). In a restricted 

 sense, the vertical plates which divide the somatic cavity of a Sea-anemone 

 . (Actinia) into chambers. 



Mesopodium (Gr. mesas, middle ; pons, foot). The middle portion of the 

 ' ' foot " of Molluscs. 



Mesosteenum (Gr. mesas, intermediate ; sternon, the breast-bone). The 

 middle j^ortion of the sternum, intervening between the attachment of the 

 second pair of ribs and the xiphoid cartilage (xipJiisternum). 



Mesothoeax (Gr. mesos ; and thorax, the chest). The middle ring of the 

 thorax in Insects. 



Mesozoic (Gr. mesos ; and zoe, life). The Secondary period in Geology. 



Metacarpus (Gr. meta, after ; karpos, the wrist). The bones which form the 

 " root of the hand," and intervene between the wrist and the fingers. 



Metamoephosis (Gr. meta, implying change ; morphe, shape). The changes 

 of form which certain animals undergo in passing from their younger to 

 their fully-grown condition. 



Metapodium (Gr. meta, after ; pous, the foot). The posterior lobe of the foot 

 in Molhcsca ; often called the " operculigerous lobe," because it develops 

 the operculum when this structure is present. 



Metastoma (Gr. Jiieta, after ; stoma, mouth). The plate which closes the 

 mouth posteriorly in the Crustacea. 



Metatarsus (Gr. meta, after ; tarsos, the instep). The bones which inter- 

 vene between the bones of the ankle (tarsus) and the digits in the hind-foot 

 of the hjcrher Vertebrates. 



