GENUSTHRACIA. 5 



2. THRACIA PUBESCENS, LEACH. The Downy Thracia. 

 (Collect. MASS. LAM.) 



PI. II, fig. 2. 



Th. testa ovato-oblonga, subdepressa, insequivalvi, sequilatera, albo- 

 grisea, antice rotundata, postice truncata et angulata; cardine foveolis 

 internis instructo. 



Shell ovate, oblong, transverse, equilateral, inequivalve, 

 slightly inflated, of a reddish white color, covered with a 

 browner shagreened epidermis, marked with irregular and more 

 or less numerous striae of increase. The beaks are short, and 

 that of the right valve is notched at its summit to receive that 

 of the left valve. The valves are pretty thick, rounded at 

 the anterior, and truncated at the posterior side ; the same 

 side is separated from the upper surface by an obtuse angle, 

 which arises from the posterior extremity of the beaks, and 

 which descends obliquely as far as the lower extremity of the 

 shell. The cardinal edge is rather thin, and destitute of 

 teeth ; it presents at the posterior side of the beaks an internal 

 hollow, short and thick. The hollow is oblique and bounded 

 outwardly by a little ridge, in which is inserted an external 

 ligament, whilst another strong ligament is situated in the 

 hollows of the valves. Interiorly they are white, smooth and 

 polished. There exists upon the anterior side a muscular 

 impression, long and very narrow in its middle, very near the 

 edge ; the posterior muscular impression is rounded and pretty 

 large. 



Length 3 lines. Width 1 inch 10 lines. 



This species, described by Lamarck under the name of ANA- 

 TINA myalls, is pretty common in the British seas, principally 



many fragments of shells upon the shores of that state. In my cabinet is a 

 single valve, which I picked up several years since upon the coast of 

 Maine, at Prout's Neck, a few miles from Portland, so that we may infer 

 it inhabits the whole coast of New England. TR. 



