Mussel Terms

with an extension or wing on the dorsal edge of the shell

having either the anterior or posterior margins forming are latively acute (sharp) angle

front or forward

bent in a bow or arched

the raised portion of the dorsal margin of a shell; formed by the embryonic shell around which the rest of the shell develops distally in a concentric manner

Also, the "Umbo"

the cavity on the inside of each valve leading into the beak, under the interdentum

raised ridges or undulations on the umbo

having two angles

mussels which are long-term breeders; females retain glochidia in their gills typically over the winter

a bundle of tough threads secreted by the byssal gland in the foot of a bivalve, used to anchor the bivalve to some hard substrate

teeth located between the lateral teeth in Corbiculidae and Sphaeriidae. Chevron - shaped like a wide-angled V

the graded variation in morphology exhibited by a species in mollusks from headwater areas to the mouth of the highest order stream

flattened out or pressed together

having a common center, such as ridges or loops radiating from the beak of a mussel valve

pertaining to individuals or populations of the same species

marked by wrinkles or ridges and grooves

shaped like the figure of the crescent moon with a convex and a concave edge

to remove the outer covering, in mollusks the epidermis

the middle or central portion of the exterior of a valve; distinct from the posterior slope or other areas immediately adjacent to the margin of the valve

round and flat like a disc

the top or back; in mussels, the hinge area

lacking both pseudocardinal and lateral teeth

spread out broadly

elongated, having the formof an ellipse

long or extended

having a shallow notching at the margin

this status at the state level includes peripheral forms which may be common in another part of its range, but whose continued existence within the political boundaries of the state is in danger of extirpation. At the national level, this status means the organism is in danger of extinction, and included on or being considered for the U.S. List of Endangered Fauna and Endangered and Threatened Plant Species of the United States, under the Endangered Species Act of 1973 (Cooper et al., 1973:x).

exterior or outside (corneous) layer of the shell

a species which has no living representatives; all individuals are no longer extant

the extinction of a species within a portion of its range

an animal with questionable taxonomic status; that is, one exhibiting variation but the extent or degree is not well enough known to determine whether it is a species, subspecies or simply individual or population variation

tapering toward each end

a thin plate-like paired structure within the mantle cavity, which serves as a respiratory organ in aquatic mollusks and in female unionids all of the gills or certain portions of the gills serve as the marsupium

globe-like, spherical

the bivalve larvae of unionids which are generally parasitic on the gills of fish

a female that has embryos in the marsupium

compact lines of temporarily arrested growth or rest periods appearing on the epidermis of the shell as a raised or darker concentric line

an elastic, elongate, corneous structure that unites the two valves dorsally along the hinge plate

single specimen designated as the "type" by the author inthe publication of a new species level taxon. Inequilateral - ina bivalve, having the two ends unequal, i.e., one end is wider or thicker than the other

moderately to greatly inflated.

a flattened area of the hinge plate between the pseudocardinal and lateral teeth

showing colors like those of a rainbow

termdescribing teardrop-shaped pustules

the elongated, raised and interlocking structures along the hinge line of the valve

one of a series of syntypes that, subsequent to the publication of an original description of a species level taxon, is selected (by publication) to serve as the type specimen for that taxon

depressed area immediately anterior to the umbo

a section ofthe posterior ventral margin of the female unionid shell which is enlarged orinflated to provide space for expansion of the marsupium with the development of the glochidia

in unionids, a brood pouch for eggs and developing glochidia, formed by a restricted portion of the outer gill, the complete outer gill or all four gills.

the area of attachment of a muscle to the inside of the shell; e.g., the anterior adductor muscle scar is the location of attachment for the anterior adductor muscle.

the interior iridescent,thin layer of a mussel shell.

formerly a tribe of Mollusca nearly equivalent taxonomically to the family Unionidae, often used as a synonymof unionid

a small rounded mass of irregular shape

slanting; angled, butnot horizontal or vertical

ovate

having the formof an orb; circular or nearly circular in outline

egg-shaped, broadly elliptical

an indented groove or line approximately parallel with the ventral margin of a bivalve shell that marks the line of muscles attaching the mantle to the shell

each specimen of a type series other than the holotype designated in the original publication of the taxon.

the external boundary on a surface, edge

see epidermis

parallel ridges on the surface of the shell.

hind or rear

a ridge on the exterior of a mussel shell, extending from the umbo to the posterior margin

the area across the dorsal portion of the valve extending from the umbo to the posterior margin, often above the posterior ridge

triangular-shaped hinge teeth near the anterior -dorsal margin of the shell.

small, raised structure on the external oroutside surface of the shell (see also tubercle)

square, or nearly square in outline

a groove or depression; in naiads a groove running from the umbo area toward the shell margin.

proceeding outward from a central point

seldom appearing, occurring widely separated in space; extremely few in number

a shape with four sides possessing four right-angles

see growth lines

having generally four distinct sides, two sides being longer than the others

a partial or incomplete circle

notched or grooved

a condition in which males and females of the same species are morphologically different, usually indicated by an expanded posterior marsupial area in the female in contrast to a more pointed or bluntly rounded area in the male

a character of some unionids that have a depression above or below the posterior ridge

shells that are thick and heavy

This status covers cases where the organism exists in small populations over a broad range, may be over exploited which may pose a threat, the organism are especially vulnerable to specific pressures, or any other reasons identified by experienced researchers (Cooper et al., 1973:x)

group of interbreeding natural populations that are reproductively isolated from all other such groups

impressed or raised lines on a shell

having striae

a geographically defined aggregate of local populations within a species that differ morphologically and/or physiologically from other aggregations of local populations within that species.

a longitudinal furrow or depression

pertaining to populations of two or more closely related species that occupy identical or broadly overlapping geographical areas

one of a series of specimens of the same taxon that formed the material studied by the original author to describe a new species level taxon, form which no type specimen (holotype) was designated

mussels which are short-termbreeders; i.e., glochidia are found in the gills of the female only during the summer

any formal taxonomic unit or category of an organism; e.g., a species or genus

This statusat the state level includes forms that are likely to become Endangered in the foreseeable future ifcertain conditions are not met. This includes forms that exhibit a considerable decrease in numbers beyond normal populations fluctuations or a documented range contraction, but are not yet considered Endangered. At the national level this applies to the Endangered Species Act of 1973 (Cooper et al., 1973:x).

a shape having four distinct sides with two sides parallel

a shape having three sides and three angles, like a triangle

having the end squared off

small, raised, rounded knob on the outside of the shell

having tubercles on the outside of the shell

a designated specimen or specimens of an organism that serves as the basis for the original name and description of any species level taxon

the dorsally raised, inflated area of the bivalve shell

refers to any member of the freshwater bivalve mollusks that belong to the superfamily Unionoidea

pattern with waves; raised ridges or bars

the right or left half of a mussel (or unionid) shell

the underside or bottom