GLOSSARY. 389 



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. 



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

 wings of insects. 



NEUROPTERA (Gr. neuron, a nerve ; pteron, a wing). An order of Insects char- 

 acterised by four membranous "wings with numerous reticulated nervures 

 (e.g., Dragon-flies). 



NEUROPTERIS (Gr. neuron, a nerve ; pteris, a fern). An extinct genus of 

 Ferns. . 



NOTHOSAURUS (Gr. nothos, spurious; saum, lizard). A genus of Plesiosaurian 

 Reptiles. 



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

 oped 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 " chorda dorsalis." 



NUDIBRANCHIATA (Lat. nudus, naked; and Gr. bragchia, gill). An order of 

 the Gasteropoda in which the gills are naked. 



NUMMULINA ( Lat. nummus, a coin). A genus of Foraminifera, comprising the 

 coin-shaped " Nummulites." 



OBOLELLA (Lat. dim. of obolus, a small coin). An extinct genus of Brachio- 



pods. 



OCCIPITAL. Connected with the occipiit, or the back part of the head. 

 OCEANIC. Applied to animals which inhabit the open ocean ( = pelagic). 

 ODONTOPTERYX (Gr. odous, tooth ; pterux, wing). An extinct genus of 



Birds. 

 ODONTORNITHES (Gr. odous, tooth ; ornis, bird). The extinct order of Birds, 



comprising forms with distinct teeth in sockets. 

 OLIGOCENE (Gr. oliyos, few ; kainos, new). A name used by many Continental 



geologists as synonymous with the Lower Miocene. 



OPHIDIA (Gr. ophis, a serpent). The order of Reptiles comprising the Snakes. 

 OPHIUROIDEA (Gr. ophis, snake ; oura, tail ; eidos, form). An order of Echino- 



dermata, comprising the Brittle-stars and Sand-stars. 

 ORNITHOSCELIDA (Gr. ornis, bird ; skelos, leg). Applied by Huxley to the 



Deinosaurian Reptiles, together with the genus Compsognathus, on account 



of the bird-like character of their hind-limbs. 

 ORTHIS (Gr. orthos, straight). A genus of Brachiopods, named in allusion to the 



straight hinge-line. 

 ORTHOCERATIDJE (Gr. orthos, straight ; keras, horn). A family of the Nau- 



tilidce, in which the shell is straight, or nearly so. 

 ORTHOPTERA (Gr. orthos, straight ; pteron, wing). An order of Insects. 

 OSTEOLEPIS (Gr. osteon, bone; lepis, scale). An extinct genus of Ganoid 



Fishes. 

 OSTRACODA (Gr. ostrakon, a shell). An order of small Crustaceans which are 



enclosed in bivalve shells. 



OTODUS (Gr. ota, ears ; odous, tooth). An extinct genus of Sharks. 

 OUDENODON (Gr. ouden, none ; odous, tooth). A genus of Dicynodont Rep- 

 tiles. 

 OVIBOS (Lat. ovis, sheep ; bos, ox). The genus comprising the Musk-ox. 



PACHYDERMATA (Gr. pachus, thick ; derma, skin). An old Mammalian order 

 constituted by Cuvier for the reception of the Rhinoceros, Hippopotamus, 

 Elephant, &c. 



PAL^ASTER (Gr. palaios, ancient ; aster, star). An extinct genus of Star- 

 lishes. 



PALEOCARIS (Gr. palaios, ancient ; karis, shrimp). An extinct genus of Deca- 

 pod Crustaceans. 



PALEOLITHIC (Gr. palaios, ancient ; lithos, stone). Applied to the rude stone 

 implements of the earliest known races of men, to the men who made these 

 implements, or to the period at which they were made. 



