SMITH: ON XYLOPHAGA. PRZSTANS, N:SP. 029 
perhaps of special importance, may be worth noticing. In the 
present species, on the posterior margin of the valves, an elongate 
curved muscular impression is observable which is peculiarly and 
very distinctly striated. This appears to be constant in all the 
specimens examined. On the other hand, this scar in X. dorsalis 
is hardly noticeable, and quite smooth. It should also be observed 
that none of the specimens of the present species exhibit the greenish 
yellow colour on the anterior part of the valves which is often present 
in X. dorsalis. In every instance the shells are uniformly dirty 
whitish, but generally exhibit the remains of a thin, deciduous, 
dirty, olivaceous periostracum at the opposite extremity. 
O% 
“@% SR 
Dorsal shields of Xylophaga dorsalis, upper surface. 
5 under surface. 
prestans, upper surtace. 
under surface. 
” I bh) ” ” 
9» ” 
” ” ” 
With regard to the size of the two species, it should be mentioned 
that the largest dimensions of X. dorsal’s hitherto recorded are those 
given by Verkriizen, and these may be contrasted with those of the 
largest examples of X. prestans. 
X,. dorsalis. X. prestans, 
Length Sie wee 14mm. aes 18mm. 
Breadth be ane Los af IY eA 
Height Sr nies ike, 17°5 mm 
Circumference wi 44 ,, ve 60 mm. 
In concluding the account of this interesting form it may be useful 
to give a list of and to offer some remarks upon, the other known 
recent species belonging to Xylophaga. 
2. XytopHaGca Dorsatts, Turton. 
Xylophaga dorsalis: Forbes & Hanley, Brit. Moll., vol. i, p. 89, pl. F, 
fig. 2; vol iv, pl. 1, figs. 3, 4; Jeffreys, Brit. Conch., vol. iii, 
p-_ 120; pl. iv, fig. 3; vol. vy, pl. lm, fig. 4; Verkrizen, 
‘‘Norwegen, seine Fjorde und Naturwunder,” 1872, p. 85, 
and plate (frontispiece). Many other references might be 
quoted. 
Hab.—Many localities around the British Isles, Norway, Denmark, 
North of France, Bay of Biscay, several places in the Mediterranean, 
the Adriatic. It has also been quoted fossil at Karlsburg in the 
Vienna Basin. 
