MONOGRAPH Olf AMERICAN SHIPWORMS. 43 



half as long as the ventral. They are minutely denticulated at the 

 free edge. The anterior median area is rather broad and marked by 

 dental ridges which bear rather fine denticles. The ridges of this 

 area join those of the anterior portion at a little more than a right 

 angle. The middle median area forms a slightly depressed groove 

 and is crossed by the enfeebled continuations of the dental ridges, 

 which here lose their denticles and form U-shaped curves. There 

 are finer incremental lines between the heavier. The posterior 

 median portion is about as wide as the anterior, and is crossed by 

 the continuation of the lines of growth and ridges just referred to. 

 Auricle moderately prominent, not strongly differentiated from the 

 posterior median portion, marked by growth lines. Interior bluish 

 white. The anterior median portion is joined to the anterior part by a 

 somewhat thickened line. The middle median portion has an irreg- 

 ular groove bearing a knob at the ventral termination. The auricle 

 is rather prominent and joins the posterior median portion without 

 differentiation. Blade unknown. The pallets are of very irregular 

 shape. Stalk twisted and curved. The external portion of the 

 pallets is scaly and marked by rough lines. The interior is smooth. 



The type, Cat. No. 194283, U.S.N.M., was collected by Dr. C. B. 

 Adams at Jamaica. It measures : Height, 6.2 mm. ; length, 6.2 mm. ; 

 diameter, 6.2 mm. The pallet measures: Length, 6.2 mm., of which 

 1.3 mm. go to the stalk; diameter, 2.2 mm. 



The present species is differentiated from Teredo {Psiloteredo) 

 hnoxi by its entirely differently shaped pallets and also by some dif- 

 ferences in the width of the anterior median portion. 



The type is a specimen of the Jeffreys collection submitted to 

 Jeffreys by Prof. C. B. Adams, and bears the name of Teredo spatha 

 Jeffreys, from which it differs by having a much larger auricle, less 

 wide anterior median area, and entirely differently shaped pallets. 



There are several additional lots of specimens in the collection of 

 the U. S. National Museum, chiefly from the West Indies and South 

 America, which indicate that additional species of these mollusks 

 will have to be recognized when more material comes in. I refrain 

 from giving a description of them or bestowing a name upon them 

 until that time comes. 



