GLOSSARY. 139 



to the maxilla inferior of human anatomy : in Arthropoda, the upper pair of 



cephalic appendages used as jaws : among Birds, the upper and lower rostra 



of the beak are often called mandibles. 

 MARSIPOBKANCHII (ndpffiiros, a pouch ; &pdyx ia > giH s )> an order of Fishes, called 



Cyclostomi by Miiller, represented by the Lampreys and Hags. 

 MAKSUPIALIA (marsupium, a pouch), an order of Mammalia separated by Cuvier 



from the rest of his Carnassiers, and now forming the subclass Didelphia. 

 MASTODON (JUOO-TOS, breast ; oSovs, tooth), an extinct genus of Proboscidea, repre- 

 senting in America the Mammoths of the Old World, and distinguished by 



the nipple-like surface of their molar teeth. 



MAXILLA (the loug form of mala, a jaw v. AXILLA), in Vertebrata, the bone corre- 

 sponding with the Superior Maxilla of human anatomy : in Arthropoda, the 



one or two pair of limbs next to the mandibles which are modified as jaws. 

 MAXILLIPED (maxilla, pes), or " foot-jaw," applied to the modified limbs of the 



three first segments of the thorax in Crustacea. 

 MEDULLA (marrow), applied to the spinal part of the central nervous system in 



Vertebrata the spinal cord. 



MEGATHERIUM (/J.eya, great ; Qrjplov, beast), an extinct animal allied to the sloths. 

 MENISCUS (privio-Kos, dim. of \nTi\vt\, a crescent"), applied to an organ of doubtful 



function in Echinorhynchus. 



MENTUM (chin), the central and lower part of the labium of insects. 

 MEROSTOMATA 07p<fe, thigh ; ffr^ua, mouth), an order of Crustacea represented by 



the genus Limulus, the Molucca King-Crabs, alone in recent times : the order 



has been also called Xiphosura, or sword-tailed. 

 MESENTEKY (^etros, intermediate ; ivrepov, intestine), the membrane between the 



alimentary canal and the walls of the abdomen. So Meso-colon, &c. 

 MESERAic=;inesenteric. The omphalo-meseraic vessels pass from the intestine to 



the umbilical vesicle in the embryo. 

 METACARPUS (jj-erd, after; Kapnos, wrist), the bones between the carpus and 



phalanges of the anterior limb of the higher Vertebrates. 

 METATARSUS (M"(, rapa-os, the flat of the foot), the bones between the tarsus and 



phalanges of the hind limb of the higher Vertebrates. 

 MOLAR (molaris, adj. of mola, a mill), applied to those teeth in Mammals which 



are not preceded by a milk set the " grinders " in Man. 

 MOLLUSCA (fr. mollis, soft), one of the primary divisions of the Animal Kingdom 



established by Cuvier. He included in it, beside the classes now admitted, 



the Tunicata, Brachiopoda, and Cirripedia. 

 MONODELPHIA (jiovos, single ; $e\<j>vs, womb), the orders of Mammalia with a single 



uterus. 

 MON<ECIOUS (judj/os, single ; O!KOS, a house), with both sexes united in one individual, 



hermaphrodite. 

 MONOTREMATA (judvos, single ; Tprifia, fr. rtrpaivw, to pierce), an order of Mammals, 



separated from Cuvier's Edentata, and forming the subclass Ornithodclphia : 



they have only one opening for the urinary, genital and intestinal canals. 

 MYKIAPODA (pvpios, numerous ; irovs, foot), an order of Arthropodous Annulosa 



separated from the Insecta of Cuvier, and represented by the Millipedes and 



Centipedes. 



NECTOCALYX (v-tiirrfa, fr. v^a, swim ; *caAu|, cup), the swimming-bell of Hydrozoa. 

 NEMATOCYST (vfj/ua, a thread ; <ci'/ims, a bladder), the " thread-cells " found in all 



Ccelenterata and some un-allied genera of Turbellaria and Mollusca. 

 NEMATOIDEA (f>)/xa, thread ; I5os, appearance)* an order of Scoletida corresponding 



