MONOGRAPH OF AMERICAN SHIPWORMS. 39 



auricle, joining the posterior median portion in an even curve. The 

 interior is bhiish white. The junction of the anterior and median 

 parts are marked by a raised thread. The middle median part has 

 a depressed groove terminating at the ventral margin in a heavy 

 knob. The auricle joins the posterior median part without a definite 

 suture. From the prominent umbone the wide, obliquely curved 

 blade is pendant, the flat surface of which runs parallel with the 

 surface of the shell. It extends for about half the length of the 

 shell. The pallets are very large, elongate spoon-shaped. The stalk 

 is short and the blade rather long, terminating at the anterior part. 

 The blade shows a tendency to flake on the outside, the distal portion 

 being marked by a series of concentric lines on the outside. The 

 inside shows the continuation of the stalk through the center of 

 the blade. It is smooth except at the distal portion, where it is 

 marked by a series of concentric lines, and is covered by a rather 

 thick periostracum. 



The type. Cat. No. 27461, U.S.N.M., comes from Charleston, South 

 Carolina, and measures: Height, 9 mm.; length, 9 mm.; diameter, 

 9 mm. The pallets measure : Length, 14 mm., of which 3.5 go to the 

 stalk; diameter, 5 mm. 



We have seen this species in collections under the name of Teredo 

 dilatata Stimpson, from which it is, however, at once distinguished 

 by its minute auricle and much larger pallets. We have it ranging 

 from Charleston to Florida. 



TEREDO (PSILOTEREDO) SIGERFOOSI, new species. 

 SIGESFOOS SHIFWOEM. 



Plate 28, fig. 2; plate 36, fig. 1. 



1908. Teredo dilatata Sigerfoos not Stimpson, Bull. U. S. Bur. Fisheries, 

 vol. 27, 1907. 



Shell subglobular, white. The extreme anterior portion with the 

 usual sinus, covered by a narrow callus from the edge of which the 

 denticulated ridges bend downward and then evenly curve back- 

 ward in a fan-shaped manner. At the posterior extremity these 

 ridges are about one-fourth as wide as the spaces that separate them. 

 There are 47 of these, for it has been possible to count them from 

 the very beginning through the thin umbonal callus. These ridges 

 slope more abruptly dorsally than ventrally, the ventral side being 

 about twice as wide as the dorsal. They are finely denticulated at 

 the free margin. The anterior median portion is rather narrow. 

 The strongly denticulated ridges here are separated by mere im- 

 pressed lines, and they join those of the anterior area at a little 

 more than a right angle. The middle median portion forms a 

 slightly concave groove, which is crossed by the much enfeebled 



