546 BULLETIN 100, UNITED STATES NATIONAL MUSEUM 



TEREDO (UNGOTEREDO) CHAMBERLAINI, new species 



chamberlain's shipworm 

 Plate 54, figs. 1, 2; plate 57, fig. 5; plate 60, figs. 9, 10, 11 



Shell minute, thin, semitransparent. The anterior sinus is narrow 

 with a thin callus which is reflected over a small portion of the out- 

 side of the anterior part, free at the reflected edge. The anterior 

 part is crossed by slender denticulated ridges which spread fan-slmped 

 from the anterior callus where they are closely approximated posteri- 

 orly. At their posterior margin they are separated by spaces about 

 as wide as the ridges. Of these ridges 50 are present in the type. 

 These ridges are rather coarsely denticulated near the anterior margin 

 and very finely so on their free edge throughout the rest of their 

 length. The junction of the anterior and anterior median ami forms 

 an even curve. The anterior median area is moderately broad and 

 marked by very slender denticulated ridges which are separated by 

 mere impressed lines. These ridges are a little less wide than those 

 on the anterior area. Twenty-eight of them occur in a straight line 

 projected across the anterior median area from the ventral margin 

 of the anterior part. The median portion of the middle part forms 

 a slightly concave groove which extends from the umbones to the 

 ventral margin. It bears in its middle a rounded cord and is crossed 

 by the feeble continuations of the dental ridges which here make a 

 decided curve and are not denticulated. The posterior portion of 

 the middle part is about one and one-half times as wide as the ante- 

 rior and median portions combined, and is crossed by numerous lines 

 of growth which lend to it a somewhat corrugated aspect. The 

 posterior part forms a very strong, broadly expanded auricle which 

 is marked from the posterior median portion by a strong constriction. 

 It is rendered somewhat fluted by incremental lines. There is a 

 strong knob at tin 1 junction of the median and posterior part at the 

 ventral margin. Interior bluish- white. The suture of the anterior 

 and median part marked by a raised line. The middle portion of the 

 median part forms a somewhat rough depressed groove which extends 

 from the umbone to the ventral margin where it terminates in an 

 elongated knob. The posterior part projects over the posterior 

 median portion as a narrow shelf with a shallow cavity behind it. 

 There is a rather long slender oblique somewhat twisted blade which 

 extends two-thirds of the distance from the umbone to the ventral 

 knob. The pallets are paddle-shaped, the stalk being expanded bas- 

 ally with two constrictions in it that give it a somewhat nodulose 

 aspect, decidedly contracted where it joins the expanded portion of 

 the pallet. The outside of the base of the expanded portion is lunate 

 and, like the stalk, of a translucent horn color. This part appears 

 to form a cup in which two calcareous cups, which resemble the horn 



