668 GLOSSARY. 



INOPERCULATA (Lat. in, without; operculum, a lid). The division of pul- 

 monate Gasteropoda in which there is no shelly or horny plate (operculum) 

 by which the shell is closed when the animal is withdrawn within it. 



INSECTA (Lat. inseco, I cut into). The class of Articulate animals commonly 

 known as Insects. 



INSECTIVORA (Lat. insectum, an insect ; voro, I devour). An order of Mammals. 



INSECTIVOROUS. Living upon Insects. 



INSESSORES (Lat. insedeo, I sit upon). The order of the Perching Birds, often 

 called Passeres. 



INTERAMBULACRA. The rows of plates in an Echinoderm which are not per- 

 forated for the emission of the " tube-feet." 



I NTERM AXILLA or PRjEMAXiLLuE. The two bones which are situated between 

 the two superior maxillae in Vertebrata. In man, and some monkeys, the prse- 

 maxillse anchylose with the maxillae, so as to be irrecognisable in the adult. 



INTUSSUSCEPTION (Lat. intu-s, within ; suscipio, I take up). The act of taking 

 foreign matter into a living being. 



INVERTEBRATA (Lat. in, without ; vertebra, a bone of the back). Animals 

 without a spinal column or back -bone. 



ISCHIUM (Gr. ischion, the hip). One of the bones of the pelvic arch in Verte- 

 brates. 



ISOPODA (Gr. isos, equal ; podes, feet). An order of Crustacea in which the 

 feet are like one another and equal. 



JUGULAR (Lat. jugulum, the throat). Connected with, or placed upon, the 

 throat. Applied to the ventral fins of fishes when they are placed beneath 

 or in advance of the pectorals. 



KAINOZOIC (Gr. kainos, recent ; zoe, life). The Tertiary period in Geology, 



comprising those formations in which the organic remains approximate 



more or less closely to the existing fauna and flora. 

 KERATODE (Gr. keras, horn ; eidos, form). The horny substance of which the 



skeleton of many sponges is made up. 

 KERATOSA. The division of Sponges in which the skeleton is composed of 



keratode. 



LABIUM (Lat, for lip). Restricted to the lower lip of Articulate animals. 



LABRUM (Lat. for lip). Restricted to the upper lip of Articulate animals. 



LABYRINTHODONTIA (Gr. laburinthos, a labyrinth ; odous, tooth). An extinct 

 order of Amphibia, so called from the complex microscopic structure of 

 the teeth. 



LACERTILIA (Lat. lacerta, a lizard). An order of Reptilia comprising the 

 Lizards and Slow-worms. 



L^EMODIPODA (Gr. laimos, throat; dis, twice ; podes, feet). An order of Crus- 

 tacea, so called because they have two feet placed far forwards, as it were 

 under the throat. 



LAMELLIBRANCHIATA (Lat. lamella, a plate; Gr. bragchia, gill). The class of 

 Mollusca, comprising the ordinary bivalves, characterised by the possession 

 of lamellar gills. 



LAMELLIROSTRES (Lat. lamella, a plate ; rostrum, beak). The flat-billed 

 Swimming Birds (Natatores), such as Ducks, Geese, Swans, &c. 



LARVA (Lat. a mask). The insect in its first stage after its emergence from 

 the egg, when it is usually very different from the adult. 



LARYNX. The upper part of the windpipe, forming a cavity with appropriate 

 muscles and cartilages, situated beneath the hyoid bone, and concerned in 

 Mammals in the production of vocal sounds. 



LENTICULAR (Lat. lens, a bean). Shaped like a biconvex lens. 



LEPIDOPTERA (Gr. lepis, a scale ; pteron, a wing). An order of Insects, com- 

 prising Butterflies and Moths, characterised by possessing four wings which 

 are usually covered with minute scales. 



LEPIDOTA (Gr. lepis, a scale). Formerly applied to the order Dipnoi, con- 

 taining the Mud-fishes (Lepidosiren). 



