218 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Subgenus Teredo Linnaeus. 
Teredo beachi Bartsch, 1920. 
Proc. Biol. Soc. Washington, 34:29, 30. 
Shell subglobular, with a strong posterior auricle. Exterior milk 
white, excepting the umbos and a streak in the median middle portion, 
which are rose colored; interior bluish white. The anterior portion forms 
a deep sinus, which is bordered by a narrow smooth edge, the external 
margin of which is reflected over the anterior portion as a smooth callus, 
which is translucent and permits the dental ridges covered by it to be 
seen through it. The dental ridges radiate from this anterior smooth 
portion fan-shaped backward over the rest of the anterior area. There 
are about thirty-five of these in the type, although some of the earlier ones 
may have been lost through the erosion of the umbos. The dental ridges, 
which are finely denticulated at their free margin, are about one-third as 
wide as the flattened spaces that separate them at the junction of the 
anterior with the median portion. The flattened interspaces are finely 
striated, the striations coinciding with the dental ridges. The dental ridges 
of the anterior portion meet those of the anterior median portion at almost 
right angles. The dental ridges of the anterior median portion are closely 
crowded, being separated by a mere line only. They are very strongly 
denticulated. The middle median portion is a somewhat depressed area, 
which extends from the umbo to the ventral margin. There is a strongly 
impressed line marking the center of this area, which is crossed by rather 
rough, curved incremental lines which extend equally rough over the pos¬ 
terior median portion. The posterior portion forms a strong auricle, which 
is marked by rough lines of growth. The interior has the umbos strongly 
curved inward, forming a prominent knob, from the inside of which a 
strong, broad, thin blade extends, which maintains almost an equidistance 
from the inside of the shell throughout its entire length, the broad side of 
the blade being placed obliquely to this. The junction of the anterior and 
median portion is marked by a slightly thickened ridge on the inside. The 
center of the median portion is marked by a roughened area which extends 
from the umbos to the ventral margin, where the usual strong knob is 
present. The auricle extends over the posterior median portion and forms 
a narrow, thin, free shelf, with very little of a cavity behind it. The auricle 
is marked by strong, curved lines of growth. The pallets are spatulate, 
very short stalked and very broad, the distal portion being decidedly 
hollowed out, almost suggesting a basal joint of Bankia . Type measures: 
height, 5.5; length, 6; diameter, 7 mm. (Bartsch.) 
Type in U. S. N. M., No. 341155. Type locality, San Pablo Bay, 
California. 
Range. California ? 
