538 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



They increase in size regularly from the anterior margin backward. 

 At the posterior termination they are about as broad as the spaces that 

 separate them. The anterior median portion is rather broad and is 

 marked by dental ridges which are as wide as those on the anterior 

 area, but a little more closely spaced and provided with much stronger 

 denticles. Of these ridges 14 can be counted in a line parallel to the 

 ventral border of the anterior portion. The median portion of the 

 middle part is narrow and slightly concave, crossed by the curved 

 continuations of the dental ridges of the anterior median portion, 

 which here lose their denticles. The posterior median portion is 

 narrow and marked by rather coarse lines of growth, the coarser of 

 which coincide with the coarser crossing the median portion. The 

 posterior and middle median portions arc not quite as wide as the 

 anterior median portion. No auricle is visible externally. It is pos- 

 sible that this may be eroded in the specimens at hand. Interior bluish 

 white. The anterior and median portions are joined by a cord. The 

 middle median portion appears as a roughened groove, which bears the 

 usual strong knob at its ventral termination. The posterior part laps 

 over the middle part as a heavy callus, which is free at the inner bor- 

 der. This portion is marked by slender parallel threads which gives 

 it a somewhat fluted appearance. A slender, somewhat irregular 

 curved blade extends from under the unbones over two-thirds of the 

 shell. The usual knob is present at the ventral margin of the median 

 part. The cone-in-cone shaped segments of the pallets are of rather 

 a peculiar shape. They appear as a series of scoops in which the 

 outer margin is only about one-fifth as high as the inner margin. The 

 free border of the inner margin forms a convex curve while the 

 free margin of the outer border joins the inner portion in an even 

 concave curve. 



The type (Cat. No. 310973, U.S.N.M.) was taken from a piece of 

 wood collected during the United States Bureau of Fisheries Steamer 

 Albatross Philippine Expedition, at station 5252, in 28 fathoms on coral 

 bottom off Linao Point, in the Gulf of Davao, Mindanao. It meas- 

 ures: Altitude, 1.3 mm.; length, 1.2 mm.; diameter, 1.3 mm. Length 

 of pallets, 3 mm., of which 0.7 mm. go to the stalk; diameter of 

 pallets, 1 mm. 



Several additional pallets from the same piece of wood are entered 

 as Cat. No. 310974, U.S.N.M. 



Genus TEREDO Linnaeus 



1758. Teredo Linnaeus, Syst. Nat., ed. 10, p. 651. 

 1922. Teredo Bartsch, Bull. 122, U. S. Nat. Mus., p. 17. 



In this genus the pallets are either paddle or spoon shaped. They 

 may be distally cupped or not, or they may even bear a calcareous 

 knob at the terminal portion. 



Type. — Teredo navalis Linnaeus. 



