26 BULLETIN 122, UNITED STATES NATIONAL MUSEUM. 



In the specimen before us it extends only about one-third of the way 

 across the shell. The pallets have a long, somewhat enfeebled cylin- 

 dric stalk which is about twice as long as the blade. The blade con- 

 sists of a calcareous club-shaped portion surmounted by a double- 

 pointed horny portion at the summit. 



Jeffreys's material, one of the cotj^pes of which we have here de- 

 scribed and figured. Cat. No. 194268, U.S.N.M., was obtained from 

 West Indian cedar {Cedrella odorata) thrown ashore, perhaps by the 

 Gulf Stream's drift at Guernsey. 



The largest of Jeffreys's specimens measures : Height, 5,5 mm. ; 

 length, 4.3 mm. ; diameter, 5.5 mm. The pallet's measure : Length, 

 3.1 mm., of which 1.6 mm. belong to the stalk; diameter, 0.7 mm. 



It is the only Lyrodus so far reported from the east American 

 waters, excepting the type of the genus, which is probably Pacific. 



TEREDO (LYRODUS) TOWNSENDI, new species. 

 TOW.XSEND SHIPWOKM. 



Plate 22, fig. 2; plate 33, fig. 2. 



1921. Teredo diegensis Kofoid not Bartsch, Rept. on the San Francisco Bay 

 Marine Piling Survey, pp. 33-36, pi. 19. 



Shell small, subglobular. white. The extreme anterior part with 

 a strong sinus covered by a heavy callus, Avhicli is reflected over part 

 of the outer portion as a thin callus, through which the dental ridges 

 may be seen. These bend suddenly downward at the anterior mar- 

 gin, and then spread fan-shaped backward, being separated by spaces 

 about three times as wide as the ridges. These ridges slope abruptly 

 on the dorsal side and much more gently on the ventral, the ventral 

 side being about twice as long as the dorsal. Of these ridges, which 

 are finely denticulated at their free margin, 22 are present in the 

 type. The anterior median area is quite narrow and marked by 

 dental ridges bearing rather prominent tubercles. These dental 

 ridges join those of the anterior part at almost a right angle. The 

 middle median portion forms a depressed groove which is crossed 

 by rough U-shaped curved wrinkles. The posterior portion is a 

 little wider than the anterior and median portion combined, and is 

 marked by a series of wavelike markings, between which finer lines 

 of growth are present. The posterior part forms a conspicuous 

 triangular auricle, which is rather large and not strongly separated, 

 though somewhat constricted at its junction with the posterior 

 median portion. The interior is bluish white. The junction of the 

 anterior and median portions is marked by a raised thread. The 

 median portion is a roughened groove at the basal termination of 

 which the ventral knob is placed. The posterior part projects over 

 the posterior median portion as a conspicuous shelf. The free auric- 

 ular portion is marked by concentric lines of growth. The umbone 



