GLOSSARY. 93 



Oper'culum (L. a lid). The bony flap which covers the gills 



of some fishes ; the disc which closes the shells of some 



Gasteropoda. 

 OpM'dia (Gr. ophis, a snake, serpent). An order of the Reptilia 



which includes the snakes. 

 Ophiuri'dea (Gr. ophis, a serpent; oura, a tail). A group of 



the Echinodermata comprising the brittle star-fishes. 

 Ophthalmic (Gr. ophthalmos, the eye). Relating to the eye, 



as the ophthalmic artery, which supplies blood to the eye. 

 OphthaTmite (Gr. ophthalmos, the eye). The short stalk on 



which each eye in the Crustacea is borne. 

 Opisthobranchia'ta (Gr. opisthen, behind; branchia, a gill). 



A series of the Branchiogasteropoda. 

 Opisthocoe'lus (Gr. opisthen, behind ; koilos, hollow). A term 



applied to those vertebrae the centra of which are concave 



behind. 

 Opisthogly'phia (Gr. opisthen, behind ; glupho, I carve, engrave). 



A group of the Ophidia having some of the posterior 



maxillary teeth grooved. 

 Opisthopul'monate (Gr. opisthen, behind ; ^L.pulmona, a lung). 



Applied to those Pulmogasteropoda which have the 



pulmonary sac situated posteriorly. 



Opistho'tic (Gr. opisthen, behind ; ous, otos, the ear). An ossi- 

 fication of the temporal bone which surrounds the fenestra 



rotunda and cochlea, and which in osseous fishes persists as 



a separate bone. 

 Opisthoto'nous (Gr. opisthe, at the back ; teino, I stretch or 



bend). A variety of the disease tetanus, in which the body 



is bent backwards. 

 Oppo'nens (L. oppono, I place opposite, oppose). A muscle 



attached to the ventral face of the carpus in the fore limb, 



and the tarsus in the hind limb, and passing to the fifth 



metacarpal or metatarsal. 

 O'ra s'erra'ta (L. notched border). The anterior indented 



border of the retina. 



O'ral (L. os, or is, the mouth). Relating to the mouth. 

 Orbicula'ris o'ris (L. round muscle of the mouth). One of the 



muscles of the mouth, also termed sphincter oris. 

 Orbicula'ris palpebra'rum (L. round muscle of the eyelids). 



One of the muscles of the eyelids which shuts the eye. 

 Orbicula'ris panni'culi (L. orbicidus, a little circle; panniculus, 



a little rag). A broad muscular band laterally encircling 



the body of the hedgehog. 



