18 BULLETIN 122, UNITP^D STATES NATIONAL MUSEUM. 



KEY TO THE AMERICAN SPECIES OF TEREDO. 



Pallets : 



Blade with the lateral margin concavely contracted at base novavgliae. 



Blade with the lateral margin not concavely contracted at base. 



Lateral margin of contracte;! base forming almost a straight line. 



Blade very narrow beaufortana. 



Blade rather broad hcfichi. 



Shell : 



Auricle with a deep dorsal sinus norangliae. 



Auricle with scarcely any sinus beachi. 



The shell of beaufortana is unknown. 



TEREDO (TEREDO) BEACHI Bartsch. 

 BEACH SHIPW0B5I. 



Plate 20, fig. 1 ; plate 32, fig. 4. 



1921. Teredo (Teredo) beachi Bartsch, Proc. Biol. Soc. Washington, vol. 

 34, pp. 29, 30. 

 Shell subglobiilar, with a strong posterior auricle. Exterior milk 

 white, excepting the umbones and a streak in the median middle por- 

 tion, which are rose colored ; interior bluish white. The anterior por- 

 tion forms a deep sinus, which is bordered by a narrow smooth edge, 

 the external margin of which is reflected over the anterior portion as a 

 smooth callus, which is translucent and pennits the dental ridges 

 covered by it to be seen through it. The dental ridges radiate from 

 this anterior smooth portion fan-shaped backward over the rest of 

 the anterior area. There are about 35 of these in the type, although 

 some of the earlier ones may have been lost through the erosion of the 

 umbones. The dental ridges, which are finely denticulated at their 

 free margin, are about one-third as wide as the flattened spaces that 

 separate them at the junction of the anterior with the median por- 

 tion. The flattened interspaces are finely striated, the striations coin- 

 ciding with the dental ridges. The dental ridges of the anterior por- 

 tion meet those of the anterior median portion at almost right an- 

 gles. The dental ridges of the anterior median portion are closely 

 crowded, being separated by a mere line only. They are very strongly 

 denticulated. The middle median portion is a somewhat depressed 

 area, which extends from the umbone to the ventral margin. There 

 is a strongly impressed line marking the center of this area, which 

 is crossed by rather rough, curved incremental lines which extend 

 equallj'^ rough over the posterior median portion. The posterior por- 

 tion forms a strong auricle, which is marked by rough lines of growth. 

 The interior has the umbones strongly curved inward, forming a 

 prominent knob, from the inside of which a strong, broad, thin blade 

 extends, which maintains almost an equidistance from the inside of 

 the shell throughout its entire length, the broad side of the blade 

 being placed obliquely to this. The junction of the anterior and 

 median portion is marked by a slightly thickened ridge on the inside. 



