30 



PHOLADIDiE. 



T. Norvagica. (From Forb. and Ilanl.) 



Valves rather solid, higher than long, the two auricles termi- 

 nating below at about the same level ; anterior auricle rather large, 



its dorsal margin concave, 

 and with fifty to sixty fine 

 radiating stria), the ante- 

 rior marginal area quite 

 narrow so that the grooves 

 arc very crowded and fine- 

 ly decussated ; posterior 

 auricle about the size of 

 the anterior, not rising so 

 high as the beaks, its dorsal margin sloping, concave, and a little 

 upturned at tip, its lower junction an obtuse angle, inner boundary 

 well defined by a shelf; umbonal blade compressed, dilated at tip. 

 Pallets spade-shaped, squared at tip, sides nearly parallel, suddenly 

 sloping to a stout, rounded stem about as long as the blade, one 

 side convex with a semilunar depressed area near the tip, the 

 other side concave, with some traces of the stem along the centre. 

 Tube solid, somewhat chambered at its entrance by ten or twelve 

 partitions. 



Height, half an inch ; length, one fourth less. 

 This is considered to be the prevailing indigenous species in 

 the Northern Atlantic Seas, but it is rare on the American coast. 

 It differs from the true T. naval is in its greater height compared 

 with length, its larger anterior and less dilated posterior auricle, 

 which latter forms its junction much higher up. The pallets are 

 larger, more solid, and not emarginate at tip. 



Teredo megotara. 



Valves as long as high, posterior auricle large and rolled outwards, its lower 

 termination much lower than the anterior auricle, no external defining furrow, 

 and no interior projecting shelf. Pallets ovate-quadrate, with a short, pointed 

 style. 



Teredo megotara, Hani.ey, Brit. Conch, i. 77, pi. 1, fig. 6 ; pi. 18, figs. 1, 2 ; iv. 247. — Jef- 

 FiiEVs, Ann. and Mag. Nat. Hist. 3d ser. vi. 121. — Sowkkby, III. Br. Shells, pi. 1, 

 fig. 3. — Tryon, Proc. Acad. Nat. Sc. Philad. (Sept. 1862), 466. 



Shell ivory white, diameters of the valves about equal ; anterior 

 triangle quite small, slightly upturned, joining the fang by a some- 

 what obtuse angle ; anterior area of fang very narrow ; this is fol- 

 lowed by a narrow segment, bounded at each margin by a furrow 



