GLOSSARY OF TECHNICAL TERMS. 351 
Opercular bones. Membrane bones of the side of the head, in fishes. 
Opercular flap. Prolongation of the upper posterior angle of the oper- 
cle, in Sun-fishes. 
Opisthocelian. Concave behind only; said of vertebrae which connect 
by ball and socket joints. 
Orbicular. Nearly circular. 
Orbit. Eye socket. 
Oscine. Musical. 
Osseous. Bony. 
Ossicula auditus. Bones of the ear in fishes. 
Osteology. Study of bones. 
Oviparous. Producing eggs which are developed after exclusion from 
the body, as in all birds. 
Ovoviviparous. Producing eggs which are hatched before exclusion, as 
in the Dog-fish and Garter Snake. 
Ovum. Egg. 
Palate. The roof of the mouth. 
Palatines. Membrane bones of the roof of mouth; one on each side 
extending outward and backward from the vomer. 
Palmate. Web-footed; having the anterior toes full-webbed. 
Palustrine. Living in swamps. 
Papilla. A small, fleshy projection. 
Papillose. Covered with papille. 
Paragnathous. Having the two mandibles about equal in length. 
Parasphenoid. Bone of roof of mouth behind the vomer. 
Paratoid. A glandular body behind the ear, in Batrachians. 
Parietal. Bone of the side of head above. 
Pectinate. Having teeth like a comb. 
Pectoral. Pertaining to the breast. 
Pectoral fins. The anterior or uppermost of the paired fins, in fishes, 
corresponding to the anterior limbs of the higher Vertebrates. 
Pelage. The hair of a Mammal, taken collectively. 
Pelagic. ULiving on or in the high seas. 
Pelvis. The bones to which the hinder limbs (ventral fins in fishes) 
are attached. 
Perforate. Pierced through ; said of nostrils when without a septum. 
Perissodactylous. Odd-toed (toes 1, 3, or 5). 
Peritoneum. The membrane lining the abdominal cavity. 
Phalanges. Bones of the fingers and toes. 
Pharyngeal bones. Bones behind the gills and at the beginning of the 
cesophagus of fishes, of various forms, almost always provided 
with teeth; usually one pair below and four pairs above. They 
represent a fifth gill-arch. 
Pharyngognathous. Having the lower pharyngeal bones united. 
Physoclistous. Having the air-bladder closed. 
Physostomous. Having the air-bladder connected by a tube with the 
alimentary canal. 
Pigment. Coloring matter. 
Pineal body. A small ganglion in the brain; a rudiment of an optic 
