215 
[Packard. 
ridges, which are well marked in the Pennsylvania examples. They 
also agree with Dawson’s description (Proc. G-eol. Soc. London, 
Dec. 20, 1865) of Nova Scotian specimens. 
Impression of an Annelid ? This impression found by Mr. Schol- 
field occurred in the black shale of the Pawtucket plant bed, and 
is 25mm. long. Its width is about 3mm., but it is not well de- 
fined, as the edges of the impression are chipped off irregularly. It 
is sinuous, there being three bends. The surface is nearly flat, and 
along the middle is a distinct furrow, which seem to prove that 
it is the impression of the under side of a worm. What seems 
to be the head-end is narrower than the rest of the body, which 
tapers somewhat to a point at the other or posterior end. There 
are no markings to suggest the lateral appendages of an annelid , 
such as a Nereid, and hence it is not possible to refer it with cer- 
tainty to the order of annelides, and yet the facies of the impression 
does not suggest anything else. 
Impressions of worms, including true Nereids,- are not uncom- 
mon in the Middle Carboniferous nodules of Mazon Creek, III., as 
we have been enabled through the kindness of Mr. Lacoe to exam- 
ine the impressions of five or six species. It would be premature 
to assign a name to the Pawtucket impression until additional 
specimens are discovered. 
Track of a mollusc. Mr. Scholfield was also fortunate enough 
to discover in the same bed a well defined track, which appears 
to be that of a gastropod mollusc ; though it may possibly be 
that of a nemertean worm. It is of uniform width and is sinu- 
ous, making three turns. It is about two inches in length, and 
uniformly about 4 mm. in width ; at one end it terminates in an 
evenly rounded flat area, which is either the beginning or end of the 
track ; the other end was broken off in collecting. The surface 
of the track is smooth and perfectly flat, uniformly so, except at 
one turn, where there is a short slight irregular median ridge, per- 
haps the result of a slight disturbance after the track was made. 
The track was apparently made by a snail, with a perfectly flat 
creeping disk, and the probabilities that it is a molluscan track 
are greater than that it was made by some nemertean worm. 
