ASTARTID^. 22 1 



Shell siiborbicnlar, compressed, thick, smooth or concentricall3^ 

 furrowed ; lunule impressed ; ligament external ; epidermis dark ; 

 hinge-teeth 2-2, the anterior tooth of the right valve large and 

 thick ; anterior pedal scar distinct ; pallial line simple. 



Animal with mantle open ; margins plain or slightly fringed ; 

 siphonal orifices simple ; foot moderate, tongue-shaped ; lips 

 large, palpi lanceolate ; gills nearly equal, united behind, and 

 attached to the siphonal band. 



The animal of Astarte borealis has mantle-margins free, plain, 

 slightl}^ cirrated in the branchial region ; united posteriorly by 

 the branchial septum, forming a single excurrent orifice ; pedal 

 muscles distinct from adductors ; gills flat, finely striated, desti- 

 tute of internal partitions; outer gill narrow, elliptical, with a 

 simple margin ; inner gill grooved, conducting to the mouth. 



ASTARTELLA, Hall and Whitney, 1858. The anterior tooth of 

 the right valve has a longitudinal pit in the summit. A. vera, 

 Hall (cxxii, 14, 15). Coal-measures ; Illinois and Indiana. 



GONiLiA, Stol., 1810. Shell orbicular, small, hinge with three 

 distinct cardinal teeth in each valve, surface with angular striae, 

 no epidermis. A. bipartita, Philippi (cxxii, 35). The round, 

 rather Lucinoid form and the angular striation of the surface 

 indicate in this species a distinct section of Astarte, similar 

 to Cyclas, a subgenus of Lucina. 



LiRODiscus, Con., 1869. Shell subquadrangular, concentrically 

 ribbed, posterior side lobed by an impressed line; hinge with 

 two cardinal teeth in each valve, right valve with a small pyram- 

 idal anterior lateral tooth, left with a posterior one distant 

 from the cardinals. Ast. tellinoides, Con. Eocene. 



RiCTOCYMA, Dall, 1871. Shell and hinge like Astarte ; sculpture 

 consisting of broken, nodulous waves, irregularly concentric, 

 covered with a thick epidermis ; equivalve and nearly equilateral. 

 A. mirabilis, Dall (cxxii, 36). Alaska. 



CRASsiNELLA, Bayle. Shell obliquely lengthened, subquadran- 

 gular. A. obliqua, Desh. Jurassic. 



PLiONEMA, Conrad, 18'72. Shell subrotund, sculptured, with 

 close radiating lines or fine ribs ; hinge of left valve with two 

 robust diverging teeth ; lunule none. A. Guerangeri, d'Orb. 



GooDALLTA (Turton, 1822), Deshayes, 1860. 



Syn. — Parastarte, Conrad, 1862. Callicistronia, Dall, 1883. 



Distr. — Recent ; Europe, U. S. Fossil, 8 sp. Eocene ; Paris. 

 G. miliaris, Defrance (cxxi, 18). 



Shell small, trigonal, equivalve, inequilateral ; valves closed; 

 cardinal teeth in the right valve two, diverging, separated by a 

 triangular socket ; in the left valve, one triangular, sometimes 

 bifid ; lateral wanting, or rudimentary ; ligament external, very 

 short ; pallial line simple. 



