JONES — TEAILS, TRACKS, AND SUEFACE-MAEKINGS. 
131 
marked footprint, and that it was of earlier date is shown by one ot 
the gallery-marks passing athwart one of its toe-prints, whilst the 
other end of the gallery has been trodden in by the last foot-mark of 
the tirst-mentioned track. 
Specimens of sandstone showing the casts of similar convex and 
concave trails are common in some of the TVealden beds * and other 
thin-bedded rocks formed in shallow water ; but the modifications are 
extremely numerous, and will require much careful observation before 
they are elucidated. Accurate drawings, at least, should be taken of 
trails and other surface-markings made by aquatic animals. Mr. A. 
Hancock's published sketches (above referred to) of the gallery-tracks 
of minute crustaceans {Sidcator arenarius and Kroeyera arenaria) 
that bore the sand of the sea-shore, are good examples of what is 
required of those who would assist the geologist to decipher the 
obscure tracks and trails (too often termed annelid-marks) by the 
light of nature. 
Mr. Poulett-Scrope, INIr. Strickland, Dr. Buckland, and Mr. Salter 
have published the results of some careful comparisons of recent 
and fossil tracks and trails ; but have not figured the recent markinnjs 
on which their conclusions rest. See Geol. Proceed., vol. i. p. 317 ; 
iv. pp. 16, 204 ; Quart. Jour. Geol. Soc, vol. x. p. 208; xii. p. 246; 
xiii. p. 199, etc. In these instances, Fishes, Crustaceans, Molluscs, 
and Worms have been quoted as the probable agents. 
In his ' Eeport on the Agriculture of New York' (' Natural History 
of New York,' Part Y.), vol. i. (1846), p. 68, etc., plates 14, 15, 16, 
Professor E. Emmons describes and figures several so-called Lower 
Palaeozoic "annelid-tracks," such as he has since referred to the trails 
of larval insects. 
Some sagacious remarks on fossil trail-prints are made in Mr. James 
Hall's ' Paleontology of New York,' 1852, vol. ii. p. 26, etc. ; and 
numerous figures of such and other surface-markings from the Silu- 
rian rocks of the State of New York are given in the plates 11 to 16 of 
that volume. f Indeed, of the so-called Eucoids illustrated by plates 
1, 2, 3, 5, 5^ 6, 7, 8, 9, and 10 of that volume, there are some that 
have been referred by ISIr. Salter to the work of Annelides. Mr. Hall 
says — " Asa fact in proof of the similarity of the trails of other animals 
to these supposed remains of Annelida, I may mention that the 
Nemapodia tenuissima of Emmons has been proved to be the trail oi 
some existing animal over the outer surface of the rock, removing the 
minute lichen which covers it, and discolouring the rock beneath." — 
J. Hall, PaliEont. New York, vol. ii. p. 32, note. 
An instance in which recent tracks have been figured in illustration 
* On the under-surface of a rippled sandstone shale from Stammerham, near Horshara, 
I have observed numerous smaD, thread-like cylinders of sandstone, forming an irregular 
reticulation, which must have been due to the fine sand, when moist, having entered 
horizontal galleries in a clay or mud beneath : after having hardened, the sand, on the 
removal of the clay, has remained in the form of delicate free cylindrical casts, attached 
by their ends to the under-surface of the slab. 
t Notes by the late Prof. E. Forbes, ou some of these figures, are appended by Mr. J. 
Hall, at page 37. 
