COEEESPONDENCE. 
455 
ing fossil surface-markings, my friend Dr. J. W. Dawson, of Montreal, 
must have been engaged in the useful labour of preserving faithful re- 
cords of the track-marks of Limiilns polyphemus on the sands of Orchard 
Beach (Gulf of St. Lawrence), for the purpose of comparing them with 
the fossil tracks, termed Protichnites and Climactichnites, found in the 
Potsdam sandstone of Canada. 
The results of these well-directed researches have been described and 
illustrated by Dr. Dawson in the Canadian ' Naturalist and Geologist ' 
for August, 1862 (vol. vii. No. 4), p. 271, etc. ; and it appears certain that 
the trail of Limulus on wet sand is very similar to Protichnites, except- 
ing that the latter has not the lateral furrows that are produced in the 
former by the edges of the carapace. Swimming in ver}" shallow water, 
Limulus produces on the sand a trail very similar to Climactichnites ; the 
latter, however, showing lateral and median ridges, whilst the former has 
furrows instead. 
Dr. Dawson agrees, therefore, with Professor Owen in referring the 
Protichnites to a Limuloid animal ; and is strongly inclined to refer Cli- 
mactichnites to the same agent. Still he thinks it not impossible that the 
large Lower Silurian Trilobite, Paradoxides, may have been the animal 
that produced all the marks in question. 
With the fact before him, that Climactichnital markings are left on a 
subaquatic surface by Limulus, Dr. Dawson, of course, rejects the hypothe- 
sis of Climactichnites being galler^'-tracks, as advanced in my paper above 
referred to Hoc. cit. p. 139). Still these recent tracks differ from what 
Dr. Dawson regards as their primaeval analogues, in that their " lateral and 
medial lines are furrows instead of ridges ;" and therefore the identifica- 
tion is not complete. I would ask that the question still remain open until 
Dr. Dawson and other good naturalists have more material at hand and a 
wider basis for conclusions. 
" I may add that the burrowing of Limulus polyphemus Dr. Dawson re- 
marks, "is easily effected in soft sand, but is confined to a mere buiying of 
itself beneath a very slight smooth elevation." The great well-known 
North American Trilobites {Paradoxides), however, whose bodies exactly 
fit in width to the Climactichnital and Protichnital trails of Canada, and 
whose abiding place Avas really the muddy sea-bed on the geological hori- 
zon of the Potsdam sandstone, in all probability crawled over these littoral 
sands, just as the Limulus frequents the existing sandy beaches in spring 
and summer; and (like Sulcator and Krceyera, loc. cit. pp. 131, 138, 139) 
it may have burrowed in them, with much longer burrows than Limulus 
makes, and in that case the in-faUen galleries would supply the raised 
ridges of the Climactichnite. 
We need not suppose the presence of Limulus, or of any unknown 
Limuloid animal, in the primordial sea ; for there is little doubt, if any, 
that Paradfxrides, known to have then existed, can have made the trails 
in question (as Dr. Dawson allows, p. 277), if they had the usual crusta- 
cean locomotive apparatus ; and "it seems almost certain, from analogy, 
that they must have possessed such organs " (Dawson, loc. cit. p. 277). 
Nor does the trail of Limulus correspond exactly with the fossil tracks ; 
the edges of its carapace produce, in crawling, side-furrows not seen in 
Protichnites ; and its subaquatic trail has but a general resemblance to 
Climactichnites, as far as we can learn from the published observations. 
Dr. Dawson, in his interesting paper before me, also notices (p. 275) the 
occurrence, at Orchard Beach, of "small Climactichnite-like tracks " that 
were made, as he ascertained, by a large beetle {Melolontha (Pohjphylla) 
variolosa ?), " which occasionally settled on the wet sand and crept for 
