GLOSSARY. 407 



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 characterized 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; saura, lizard). A genus 



of Plesiosaurian Reptiles. 

 NOTOCHORD (Gr. notos, 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 



" 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 Foramini- 



fera, comprising the coin-shaped " Nuinmulites. " 



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



of Brachiopods. 



OCCIPITAL. Connected with the occiput, 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; amis, bird). The extinct 

 order of Birds, comprising forms with distinct teeth in sockets. 



OLIGOCENE (Gr. oligos, 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 com- 

 prising the Snakes. 



OPHIUROIDEA (Gr. ophis, snake; our a, tail ; eidos, form). An 

 order of Echinodermata, comprising the Brittle-stars and Sand- 

 stars. 



ORNITHOSCELIDA (Gr. ornis, bird; skelo, 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. 



ORTHOCERATID/E (Gr. orthos, straight; keras, horn). A family of 

 the Nautilidce, 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 Crus- 

 taceans which are enclosed in bivalve shells. 



