Analogue. A likeness between two objects when otherwise they are totally 



different, as the wing of a bird and the wing of a butterfly. 

 Anastomosing. Coming together. 



Androgynous. Combining both sexes in the same individual. 

 Annular. Made up of rings. 

 Anterior. The front or fore end. 



Approximate. Near together, as the umbones of some Unios. 

 Aquatic. Inhabiting the water. 

 Arborescent. Branching like a tree. 

 Arched. Bowed or bent in a curve. 

 Archibenthal. The marine region lying between the deep sea (abyssal) and the 



shallow margin of the land (littoral). 

 Articulated. Jointed. 



Arcti-spiral. Tightly coiled, as some spiral shells. 



Arcuated. Bent in a bow or arched, as the ventral edge of some bivalves. 

 Asphyxiating. Causing suspended animation ; apparent death. 

 Assimilation. Act of converting one substance into another, as the changing 



of food-stuffs into living bodies. 

 Asymmetrical. Not symmetrical. 

 Atrophied. Wasted away. 



Attenuate. Long and slender, as in some shells. 

 Auditory. Connected with the hearing. 

 Auricled. Eared, or with ear-like appendages. 

 Basal. The bottom or lower part. 



Benthal. The deepest part of the sea (the same meaning as abyssal). 

 Biangulate. With two angles. 

 Bicuspid or bicuspidate. Having two cusps. 

 Bifid. Having two arms or prongs. 

 Bifurcated. Having two branches. 

 Bilateral. With two sides. 

 Bilobed. With two lobes. 

 Bisexual. Having two sexes. 



Bivalve. A mollusk with two valves or shells, as the Unio. 

 Branchial. Referring to the lower or ventral siphons in Pelecypods. 

 Bulbous. Swollen. 



Byssiferous. Attached to a byssus, as in some Unios. 

 Caducous. Falling off or shedding, as of hair. 

 Calcareous. Composed of carbonate of lime. 

 Callosity. A hardened and raised bunch, as the callus on the columella of some 



shells. 



Callus. A deposit of shelly matter. 

 Calyculate. Cup-like, as the umbo when separated from the rest of the shell 



by a distinct mark, as in Calyculina, 



Campanulate. Formed like a bell. 



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