NATUKAL IIISTOKY SOCIETY, 



155 



GLOSSARY OF MOLLUSCAN TERMS. 



Acute, sharp, as the outer lip of many 

 univalves. 



Adductor muscle, in bivalves, the one 

 or two muscles used to hold the 

 valves together ; adductor impres- 

 sions, the scars in the shell showing 

 where the muscles were attached. 



Amphibious, inlial^ting both land and 

 water. 



Anterior^ in bivalves, the tnd of 

 the shell having the foot and mouth 

 of the animal (Fig. 15, A.) ; in uni- 

 valves, the end op])osite the ajiex of 

 the spire of the sliell (Fig, 85, A). 



Aperture, an opening ; of univalves, the 

 mouth of the shell (Fig. 32, K). 



Apex, the extreme point of the spire 

 of a univalve (Fig. 32, B). 



Approximate, very near together, as 

 the umbones of some bivalves. 



Aquatic, inhabiting the water. 



Arborescent, tree-like; branching like 

 a tree, as the gills of some sea slug's 

 (Fig. 30, G), ' 



Arched, bowed, or rounded. 



Arcuate, in the form of an arch. 



Area of shell, the space included in 

 the outline of the shell as drawn ; 

 the aperture is more or less in ratio 

 to the whole. Fig. 54 shows aper- 

 ture more than two-thirds the area. 



Attenuate, long and slender, or ending 

 in a long point. 



B 



Basal, bottom ; when used in uni- 



Talves, it means the anterior end of 



the aperture (F'ig. 35, A), 

 Beaks, often used in mulluscan works 



under bivalves and equivalent to 



umbones or umbo (which see). Fig, 



5, E), 

 Bivalve, applied to shells with two 



movable plates forming sides; as 



the mussel, Plate I. 

 Boreal, northern. 

 Brackish, applied to water having a 



little salt, as the mouths of streams 



flowing into the ocean. 

 Branchia, a gill or breathing organ of 



water animals. 

 Succiniform, shaped like buccinum 



(Fig, 34), 



Bulbous, swollen or globular, 

 Byssiferous, fastened by byssus, as the 



salt-water mussels. 

 Byssus, thread-like strands which are 



used to fasten some bivalves. 



Calcareous, lime-like or formed of 

 lime. 



Callous, hardened, or covered with a 

 special deposit. 



Callus, special deposit of shell ma- 

 terial often found near the aperture 

 of univalves (Fig. 39, E). 



Calyculat', having a cup-like umbo, 

 which is divided from the rest of 

 the shell by a distinct mark, 



Camjanulate, in the form of a bell. 



Canal, a grove or channel, usually ap- 

 plied to the anterior prolongation 

 of univalve shells (Fig. 37), 



Cancellated, cross-barred; meshed with 

 lines crossing each other and form- 

 ing a lattice-like appearance (Fig, 

 45), 



Cardinal teeth, the transverse teeth of 

 bivalve shells ; found near tiie um- 

 bones (Figs. 3 and 7, C). 



Carinate, v,^ith a keel or ridge. 



Cartilage, the internal rubber-like sub- 

 stance which opens the valves of a 

 shell, 



C nulal, having a tail-like appendage. 



Cinieter, having a shape like a sword. 



Cinereous, having the color of wood 

 ashes. 



Cirrated, with movable hairs, as the 

 siphons of many bivalves ; they are 

 prehensile or grasping organs, 



Crriferous, the same as cirrated, 



Clauate, club shaped. 



Closed, applied to bivalve shells which 

 shut tightly all around the edge 

 (Fig. 6), 



Compressed, applied to bivalves when 

 the valves are quite flat. 



Concave, hollowed out. 



Concentric, from the same centre ; ap- 

 plied to the lines or grooves on bi- 

 valves which are parallel with each 

 other, and form arcs with the umbo 

 as a centre (Fig, 5). 



Columella, a small column ; the term 

 used in univalve shells for the axis 

 around which the whorls are , 



forrriArl 



