162 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. 37. 
XYLOTRYA DRYAS, new species. 
Plate 25, figs. 2, 3, 5, 6, 7. 
From the stem of a living mangrove at Estero del Palo Santo, Tumbes, Peru. 
As arule, animals belonging to this family excavate their burrows 
in dead wood, not living trees, though the African mangrove of Sene- 
gal is bored in the living state by a true Teredo, which received the 
name of T. senegalensis from Blainville. The present species so far 
as noted is the first to be reported from living trees in America, and 
the first of the genus Xylotrya known to have this habit. 
The external surface of the valves, beginning in front, is divided 
into five areas, of which the first might perhaps be regarded as internal 
rather than external, though when the muscles are removed it faces 
outward. It isin reality a myophoric surface, free from periostracum 
and in life supports very powerful muscles, which hold the two valves 
together; the surface of this area is rather irregular, the dorsal ex- 
tremes of the area in the two valves project in blunt points; this area 
is separated from what is generally called the anterior area of the 
valves by a deep sulcus, the posterior slope of which terminates in a 
rounded bounding ridge; the anterior area proper is concentrically 
sculptured by regular, low, sharp, equally spaced, fine lamelle with 
slightly wider interspaces; these are crossed by extremely sharp, fine, 
close, microscopic, radial strive; the vertical width of this area is a 
little more than the width of the premedian area; the sculpture 
changes abruptly at -the junction of the two areas and the angle at 
the junction of their ventral margins, as of the sculpture, is about 97°. 
The premedian area is similarly sculptured, but the lameile are rather 
smaller and more close set than in the anterior area, while the radial 
striz are coarser and deeper, showing distinctly on the tops’ of the 
lamelle. The postmedian area is feebly concentrically striated, cov- 
ered with a thin glossy periostracum and more or less brown stained 
by the mangrove sap; it is separated from the posterior lobe by an 
angle; the posterior lobe or area is similar in surface and forms some- 
what less than a semicircle, low and evenly rounded. The two valves 
are held together by strong muscles, chiefly attached to three myo- 
phoric areas. The first of these, anterior and looking outward and 
forward, has been described; the second forms an irregular concavely 
excavated rough surface extending from the anterior sulcus to the 
angle between the postmedian and posterior lobes of the shell. This 
surface includes much of the dorsal edges of the original valves, and 
when the muscles are removed the appearance is as if the valves have 
been badly eroded, but the condition is the same in the youngest 
valves I have been able to examine, and if, as seems evident, a con- 
siderable portion of the umbonal surface is missing, it has unques- 
tionably been removed by absorption, and not by external erosion. 
The styloid processes are broad and long, extending nearly to the 
