24 BULLETIN 122, UNITED STATES NATIONAL MUSEUM. 



paneled blade is hollow throughout its length, the cavity being 

 divided into two chambers by a median septum. 



The type and some additional specimens, Cat. No. 341129, U.S.N.M., 

 come from a small piece of wood collected by the United States Coast 

 Survey steamer Blake at Station 192, in 138 fathoms off Dominica, 

 West Indies. The type measures : Length, 2.3 mm. ; altitude, 2.2 mm. 

 The pallet measures: Length, 2.5 mm., of which 1.2 mm. belong to 

 the stalk. Width of pallet, 1.1 mm. 



Subgenus Lyrodus Gould. 



1S70. Lyrodus Gould, Invert. Mass., p. 34. 

 In this subgenus the terminal portion is not cupped, but ends in 

 two lateral forks, covered with a periostracum. 

 Type. — Teredo {Lyrodus) cldorotica Gould. 



KEY TO THE AMERICAN SPECIES OF LYRODUS. 



Pallets : 



Blade broadly ovate bipartita. 



Blade elongate ovate toivnsendi. 



Shell : 



Anterior portion of median part very broad bipartita. 



Anterior portion of median part very narrow toivnsendi. 



TEREDO (LYRODUS) CHLOROTICA Goul^. 



1870. Teredo chlorotica Gould, Invert. Mass., pp. 33-34. 



I have not seen specimens of this species and quote Dr. A. A. 

 Gould's statement: 



" Shell minute, subglobose, greenish, the anterior area of the claw 

 very large; pallets with the blades lyre-shaped, posterior portion 

 encrusted. 



" Shell quite small, solid, subglobose, valves rhomboidal, greenish, 

 beaks enveloped in the callus of the triangular area, which is large, 

 ascendant, obtuse at point, with about 40 diverging square ribs, the 

 interspaces finely barred; marginal area of the claw very broad, the 

 ridges as broad as those of the anterior wing and coarsely barred, 

 but the interspaces very narrow; at the junction of the two series 

 is a deep diagonal groove toward which they slope; a sharp angle 

 limits the anterior area, followed by a barred groove ray, then a 

 verj^ narrow posterior area with a lunate auricular projection, occu- 

 pying about the middle third of the posterior margin, not reflected, 

 its inner face concave and broadly shelving over the deep cavity of 

 the beaks ; no callosity to beaks ; denticle slender, blade attached close 

 to the denticle, linear, somewhat granulate. Pallets paddle-shaped, 

 the stalk flexuous and very delicate, the blade half as long as the 

 .stalk, lyre-shaped, the extreme two thirds covered with a dark crust 

 which has a projecting horn at each angle; when the crust is de- 



