GLOSSARY. 377 



Homocercal. Referring to fishes the lobes of whose tails are equal, 

 as the perch. 



Homology. Applied to parts which are structurally alike. 



Hydridae. An order of Hydrozoa. 



Hydrozoa. A class of Coelenterata. 



Hymenoptera. (Gr. fyiV> hymen, or membrane ; irrfp6v t wing.) An 

 order of insects having two pairs of membranous wings. 



Hyoid. The bone which supports the tongue ; so called from its 

 resembling the letter U in man. 



Ichthyosaura. An extinct genus of Reptilia. 



Imago. (Lat. an image.) The perfect form of insects. 



Inequilateral. Applied to shells having the two ends unequal. 



Inequivalve. Having two unequal valves. 



Infusoria. (Lat. in, on ; fundo^ I pour.) A class of Protozoa. 



Isopoda. (Gr. fcros, equal ; irous, foot.) An order of Crustacea. 



Labium. (Lat. lip.) The lower lip in the Arthropoda. 



Labrum. (Lat. lip.) The upper lip in the Arthropoda. 



Lamellibranchiata. (Lat. lamella, a leaf or sheath ; branchia, gill.) 

 Mollusks having large, leaf-like gills. 



Larva. (Lat. a mark.) The second stage of an insect, as the cater- 

 pillar, etc. 



Lepidoptera. An order of insects. 



Lithocysts. The sense-organs of certain jelly-fish. 



Longipennata. (Lat. longtts^ long ; penna, wing.) A group of 

 birds. 



Lucernarida. (Lat. hicerna, a lamp.) An order of Hydrozoa. 



Lumbar. (Lat. lumbus, a loin.) Belonging to the loins. 



Macrura. A group of decapod crustaceans. 



Madreporic. Containing many pores or cells. 



Mandible. (Lat. mandibulum, a jaw ; fr. mando, I chew.) The up- 

 per jaw of Insecta ; the lower jaw of Vertebrata. 



Marsupium. A pouch. 



Marsupialia. (Lat. marsupium, a pouch.) An order of Mammalia. 



Maxillipedes. (Lat. maxilla, jaws ; pes, foot.) The modified limbs 

 of Crustacea, used as masticatory organs. 



Megalops. One of the stages of the young crab. 



Merostomata. An order of Crustacea. 



Mesenteries. (Gr. /teVos, the middle ; Zvrepov, an intestine.) The 

 vertical partitions which divide into chambers the intervening 

 _ space between the alimentary tube and the body-wall of a sea- 

 anemone. 



Mesothorax. The middle segment of the thorax in insects. 



