GLOSSARY OF TECHNICAL TERMS CXX1X 



Mandible. The lower jaw. (Fig. 1, md.) 



Maxillary. The posterior element of the lower jaw. '(Fig. 1, mx.) 



Metapterygoid. One of the chain of bones connecting'the lower jaw with the skull. 



Molar. With a flattened, grinding surface. Said of teeth. 



Mucijerous. Producing or containing mucus. 



Muscular impressions. The visible diagonal lines or grooves marking externally 

 the intervals between the muscle plates. (See myotome.) 



Muzzle. The anterior extremity of the head. 



Myotome. A muscle plate. (See muscular impressions.) 



Nape. The part of the neck next to the occiput. (Fig. 1, np.) 



Nasal. A bone of the nose. 



Neural spine.- The upper spine of a vertebra. 



Notochord. The embryonic cartilaginous vertebral column, persistent in lampreys, 

 sharks, and rays, and most ganoids. 



Nuchal. Pertaining to the nape. 



Obsolete. All but disappeared ; only faintly apparent. 



Occiput. The back of the head. 



Ocellus. An eye-like spot. 



Opercle. The gill-cover. (Fig. 1, o. See operculum.) 



Operculum. A bone of the side of the head, forming the major portion of the cover- 

 ing of the gill cavity. 



Opercular flap. A backward prolongation of the posterior angle of the opercle. 

 (Fig. 62, 63.) 



Opercular gill. A rudimentary gill on the lower inner face of the operculum in gars 

 and sturgeons. It is a true gill, receiving venou&blood, in which respect it dif- 

 fers from a pseudobranch. In the gars, in which there is both an opercular gill 

 and an exposed pseudobranch, meeting at an angle on the inner face of the 

 operculum, the opercular gill may be recognized by its inferior position and by 

 the downward and backward direction of its gill-filaments. (See pseudo- 

 branch.) 



Opisthoccelian. Concave behind only; said of the ventebra? of gars, which connect 

 by ball and socket joints, as in reptiles. 



Orbit. The bony eye-socket. 



Ossicula auditus. (See Weberian ossicles.) 



Palatine. A paired bone of the roof of the mouth. (Fig. 56, pi.) 



Papilla. A small fleshy projection. 



Papillose. Covered with papillas. 



Parietal. One of the roofing bones of the skull. 



Pectinate. Having teeth like a comb. 



Pectoral. Pertaining to the breast. 



Pectoral arch. (See shoulder girdle.) 



Pectoral fins. The anterior or uppermost of the paired fins. (Fig. 1, p.) 



Pectoral girdle. (See shoulder girdle.) 



Pelvic arch, or girdle. The bones to which the ventral fins are attached; pubic 

 bones. 



Peritoneum. The membranous inner lining of the abdominal cavity. 



Pharyngeal bones. Bones representing a fifth gill-arch, behind the gills, opposed to 

 each other, usually in several upper and one lower pairs, as masticatory struc- 

 tures, for which purpose they are, as a rule, armed with teeth. (Fig. 57, lph, 

 and Fig. 56, uph.) 



Pkysostomous. Having the air-bladder connected with the cesophagus by an open 

 duct. 



Plectospondylous. Having the anterior vertebrae modified and furnished with Webe- 

 rian ossicles. (See Weberian ossicles.) 



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