40 BULLETIN 122, UNITED STATES NATIONAL MUSEUM. 



continuations of the dental ridges of the anterior portion, which 

 make a U-shaped bend here, becoming lost at the posterior margin. 

 Between these stronger ridges finer rough lines which coincide with 

 the other are present. The posterior median portion is a little wider 

 than the anterior, and the middle portion and is marked by rough 

 wavelike markings. The posterior part forms a small auricle, which 

 joins the posterior median portion without specific differentiation. 

 The interior is bluish white, the anterior and median portion being 

 joined by a cordlike callus. The middle median portion bears a 

 groove, at the ventral margin of which the usual knob is present. 

 The auricle joins the posterior median portion without any sutural 

 marking. The umbonal knob is strong, and from the inside of it 

 a broad, curved blade extends two-thirds of the way across the in- 

 side of the shell. The pallets are spoon-shaped. The stalk is irreg- 

 ular and twisted, short, and can be seen extending through the 

 blade on the inside. The blade is broadly ovate, solid and smooth 

 when viewed from the inside, except at the distal end, which is 

 marked by a number of concentric lines. The outside is inclined 

 to scale, the distal margin being marked by a series of concentric 

 growth lines. 



The type, Cat. No. 345357, U.S.N.M., was collected by Sigerfoos 

 at Beaufort, North Carolina, December 7, 1911. It measures : Height, 

 5 mm. ; length, 5 mm. ; diameter, 5 mm. The pallet measures : 

 Length, 5.3 mm., of which 1.7 mm. go to the stalk; diameter, 2.7 mm. 



This is the specimen which I identified for Prof. Charles P. Siger- 

 foos as Teredo dilatata. I take great pleasure in naming it for 

 Professor Sigerfoos, who has contributed more to the life history 

 of American shipworms than any other man. 



This species is easily distinguished from Teredo dilatata by its 

 small auricle and broad blade. 



TEREDO (PSILOTEREDO) TRYONI, new species. 

 TRYON SHIPWORM. 



Plate 29, fig. 3; plate 35, fig. 4. 



Shell subglobular, white. The anterior area with the usual sinus 

 and callus. The extreme anterior basal portion projects as a tri- 

 angular point. A callus is reflected over the anterior area, but 

 closely appressed to it and not strongly differentiated from it. The 

 dental ridges curve suddenly downward and then spread out evenly 

 in a fanlike manner. They are separated at their posterior ter- 

 mination by spaces a little wider than the dental ridges. These 

 ridges are strongly denticulated at the free margin and slope a little 

 more abruptly dorsally than ventrally. The type, which has the 

 umbone quite strongly eroded, shows 58 of these ridges. The an- 



