GLOSSARY 329 



which can be drawn across the eye in Birds and Rep- 

 tiles, either to moderate the effects of a strong light or to 

 sweep particles of dust, etc., from the surface of the eye. 



Ocelli. — The simple eyes or stemmata of Insects, usually 

 situated on the crown of the head between the great 

 compound eyes. 



(Esophagus. — The gullet. 



Oolitic. — A great series of secondary rocks, so called from 

 the texture of some of its members, which appear to be 

 made up of a mass of small egg-like calcareous bodies. 



Operculum. — A calcareous plate employed by many Mol- 

 lusca to close the aperture of their shell. The opercular 

 valves of Cirripeds are those which close the aperture of 

 the shell. 



Orbit. — The bony cavity for the reception of the eye. 



Organism. — An organized being, whether plant or animal. 



Orthospermous. — A term applied to those fruits of tho 

 Umbelliferas which have the seed straight. 



Osculant. — Forms or groups apparently intermediate 

 between and connecting other groups are said to 

 be osculant. 



Ova. — Eggs. 



Ovarium or Ovary (in plants).— The lower part of the 

 pistil or female organ of the flower, containing the 

 ovules or incipient seeds; by growth after the other 

 organs of the flower have fallen it usually becomefj 

 converted into the fruit. 



Ovigerous. — Egg-beariog. 



Ovules (of plants). — The seeds in the earliest condition. 



Pachyderms. — A group of Mammalia, so called from their 

 thick skins, and including the Elephant, Rhinoceros, 

 Hippopotamus, etc. 



Paleozoic. — The oldest system of fossiliferous rocks. 



Palpi. — Jointed appendages to some of the organs of the 

 mouth in Insects and Crustacea. 



