Three New Species of Teredo 3 
Internally, in the left valve a short, broad, flat hinge 
plate, directly beneath the umbone. The blade slightly 
more than one-half the length of the shell, of nearly uni- 
form width for its entire length, the lower half reflected 
posteriorly. The ventral knob large. The internal shelf 
of the auricle well marked. 
Pallets (fig. 3) of the type of Teredo navalis Linné. 
The stalk of about the same length as the blade, and 
merging into it by a gradual curve. The lower half of 
the blade white, the calcareous part of the upper half, 
as seen through the transparent chitinous covering, 
slightly cupped, the lateral portions extending farther 
distally than the median. The upper half entirely com- 
posed of transparent, yellowish horn-colored periostra- 
eum, which is deeply cupped distally for more than half 
its length, the outer surface being slightly less deeply 
cupped than the inner, and with a deep, narrow sinus - 
at the center, 
The posterior end of the tube with two short, nar- 
row, low ridges arising from opposite sides of the in- 
ternal wall; these ridges continue posteriorly beyond 
the shelly portion of the tube as sharp points. 
The type specimen (Mus. Comp. Zodl., 45303) is from 
San Juan, Porto Rico. Additional specimens from the 
type locality are also in the U. S. National Museum. 
The measurements of the type are: 
Total length of tube 40 mm. 
Shell, height 3.2 mm., length 3.1 mm. 
Pallets, length 3.8 mm., divided equally between 
blade and stalk, width of blade 0.8 mm. 
Teredo portoricensis is more closely related to Teredo 
bartschi Clapp than to any other described species. The 
variation of the shell characters in each species is so 
great that only very slight constant differences can be 
