8o6 GLOSSARY. 



(Lamellibranchiata) in which the shell is closed by a single adductor 



muscle. 

 MONOPHYODONT (Gr. monos ; phuo, I generate ; odous, tooth). Applied to those 



Mammals in which only a single set of teeth is ever developed. 

 MONOTHALAMOUS (Gr. inonos ; and thalamos, chamber). Possessing only a 



single chamber. Applied to the shells of Foraminifera and Mollusca. 

 MONOTREMATA (Gr. monos ; trema, aperture). The order of Mammals corn- 

 prising the Duck-mole and Echidna, in which the intestinal canal opens 



into a "cloaca" common to the ducts of the urinary and generative organs. 

 MULTILOCULAR (Lat. multus, many ; loculus, a little purse). Divided into 



many chambers. 



MULTIVALVE. Applied to shells which are composed of many pieces. 

 MULTUNGULA (Lab. multus, many; ungula, hoof). The division of Perisso- 



dactyle Ungulates, in which each foot has more than a single hoof. 

 MYELON (Gr. muelos, marrow). The spinal cord of Vertebrates. 

 MYRIAPODA or MYRIOPODA (Gr. murios, ten thousand ; podes, feet). A class 



of Arthropoda comprising the Centipedes and their allies, characterised by 



their numerous feet. 



NACREOUS (Fr. 'nacre, mother-ofcpearl, originally Oriental). Pearly ; of the 

 texture of mother-of-pearl. 



NATATORES (Lat. nare, to swim). The order of the Swimming Birds. 



NATATORY (Lat. nare, to swim). Formed for swimming. 



NAUTILOID. Resembling the shell of the Nautilus in shape. 



NECTOCALYX (Gr. necho, I swim ; kalux, cup). The swimming-bell or "disc" 

 of a Medusa or Jelly-fish, 



NEMATELMIA (Gr. nema, thread ; helmins, a worm). The division of Scolecida 

 comprising the Round-worms, Thread-worms, &c. 



NEMATOCYSTS (Gr. nema, thread ; kustis, a bag). The thread-cells of the 

 Coelenterata. (See Cnidse.) 



NEMATOIDEA (Gr. nemo,, thread ; eidos, form). An order of Scolecida com- 

 prising the Thread- worms, Vinegar-eels, &c. 



NEMATOPHORES (Gr. nema, thread ; phero, I carry). Csecal processes found on 

 the coenosarc of certain of the Sertularida, containing numerous thread-cells 

 at their extremities. 



NEMERTIDA (Gr. Nemertes, proper name). A division of the Turbellarian 

 Worms, commonly called " Ribbon -worms." 



NERVURES (Lat. nervus, a sinew). The ribs which support the membranous 

 wings of insects. 



NEURAL (Gr. neuron, a nerve). Connected with the nervous system. 



NEURAPOPHYSIS (Gr. neuron, a nerve ; apophusis, a projecting part). The 

 " spinous process " of a vertebra, or the process formed at the point of junc- 

 tion of the neural arches. 



NEUROPODIUM (Gr. neuron, a nerve ; pous, the foot). The ventral or inferior 

 division of the "foot-tubercle" of an Annelide; often called the "ventral 

 oar." 



NEUROPTFRA (Gr. neuron; andpteron, a wing). An order of insects charac- 

 terised by four membranous wings with numerous reticulated nervures (e.g., 

 Dragon-flies). 



NEUTER (Lat. neither the one nor the other). Having no fully developed sex. 



NIDIFICATION (Lat. nidus, a nest ; facio, I make). The building of a nest. 



NOCTURNAL (Lat. nox, night). Applied to animals which are active by night. 



NORMAL (Lat. norma, a rule). Conforming to the ordinary standard. 



NOTOBRANCHIATA (Gr. notos, the back ; and bragchia, gill). Carrying the gills 

 upon the back ; applied to a division of the Annelida. 



NOTOCHORD (Gr. notos, the back ; chorde, string). A cellular rod which is 

 developed in the embryo of Vertebrates immediately beneath the spinal 

 cord, and which is usually "replaced in the adult by the vertebral column. 

 Often it is spoken of as the " cliorda dorsalis." 



NOTOPODIUM (Gr. notos, the ba;.k; and pous, the foot). The dorsal division 

 of one of the foot-tubercles or parapodia of an Annelide; often called the 

 "dorsal oar." 



