GLOSSARY. 387 
Homocercat (Gr. homos, same; kerkos, tail). Applied to the tail of Fishes 
when it is symmetrical, or composed of two equal lobes. 
Hysoponts (Gr. hubos, curved ; odous, tooth). A group of Fishes of which 
Hybodus is the type-genus. 
Hyprowa (Gr. hudra; and eidos, form). The sub-class of the Hydrozoa, 
which comprises the animals most nearly allied to the Hydra. 
Hyprozoa (Gr. hudra ; and zoém, animal). The class of the Calenterata which 
comprises animals constructed after the type of the Hydra. 
HYMENOPTERA (Gr. humen, a membrane; pteron, a wing). An order of In- 
sects (comprising Bees, Ants, &c.) characterised by the possession of four 
membranous wings. 
ICHTHYODORULITE (Gr. ichthus, fish ; dorus, spear ; lithos, stone). The fossil 
tin-spine of Fishes. 
ICHTHYOPTERYGIA (Gr. ichthus ; pterux, wing). An extinct order of Reptiles. 
IcHTHYORNIS (Gr. ichthus, fish; ornis, bird). An extinct genus of Birds. 
ICHTHYOSAURIA (Gr. ichthus; saura, lizard). Synonymous with IJchthyop- 
terygia. 
IGUANODON (Iguana, a living lizard ; Gr. odous, tooth). A genus of Deinosau- 
rian Reptiles. 
Incisor (Lat. incido, I cut). The cutting teeth fixed in the intermaxillary 
bones of the Mammalia, and the corresponding teeth in the lower jaw. 
INEQUILATERAL. Having the two sides unequal, as in the case of the shells of 
the ordinary bivalves (Lamellibranchiata). When applied to the shells of 
the Foraminifera, it implies that the convolutions of the shell do not lie in 
the same plane, but are obliquely wound rcund an axis. 
INEQUIVALVE, Composed of two unequal pieces or valves. 
INOCERAMUS (Gr. is, a fibre ; keramos, an earthen vessel). An extinct genus of 
Bivalve Molluscs. 
INSECTA (Lat. ixseco, 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. zxsedeo, 1 sit upon). The order of the Perching Birds, often 
called Passeres, 
INTERAMBULACRA. The rows of plates in an Echinoid which are not per- 
forated for the emission of the ‘‘ tube-feet.” 
INTERMAXILLE or PREMAXILLEH. The two bones which are situated between 
the two superior maxille in Vertebrata. In man, and some monkeys, the 
premaxille anchylose with the maxille, so as to be irrecognisable in the 
adult. 
INVERTEBRATA (Lat. in, without; vertebra, a bone of the back). Animals 
without a spinal column or backbone. 
Isopopa (Gr. isos, equal; podes, feet). An order of Crustacea in which the 
feet are like one another and equal. 
Katnozoic (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, 
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, alizard). An order of Reptilia comprising the Liz- 
ards and Slow-worms. 
LAMELLIBRANCHIATA (Lat. lamella, a plate; Gr. bragchia, gill). The class of 
Mollusca comprising the ordinary bivalves, characterised by the possession 
of lamellar gills. 
LEPIDODENDRON (Gr. lepis, ascale ; d-ndvon, a tree). A genus of extinct plants, 
so named from the scale-like scars up 1 the stem left by the falling off of the 
leaves. 
