0(1 PROCEEDINGS OF THE AMERICAN ACADEMY. 



aembling ripple marks (Fig. 3). These were produced by the Band 

 swept up by the Bwimming feet." Dr. Dawson then compares the trail 

 represented by his Fig. 3 with Logan's Climactichnites, and they are 

 remarkably similar, except that the oblique furrows made by the l< 

 between the median' and lateral ridges are directed in the reverse 

 direction. 



Of the tracks afterwards described and figured by Dr. Dawson* from 

 the upper Carboniferous of Nova Scotia, none seem to me to be referrible 

 to trilobitic or merostomatous trails. Proticluiites carbonarius, as already 

 remarked in these Proceedings, f appear to have been made by a crusta- 

 cean, and we have referred them to a distinct genus, Ostrakirhnitcs. 



Some years ago I made some experiments with small Limuli by placing 

 one in a shallow tin pan, in which the sand was about half an inch deep, 

 ami the water not deep enough to entirely cover the body. The animal. 

 so far as I can now remember, used its ambulatory feet in walking, while 

 the Bwimming or abdominal legs were partially used. The result may 

 be seen in Fig. 1. The king-cr:il> was about four inches (10 cm.) in 

 width. The trail it made consisted, besides the tracks themselves, of an 

 outer ridge made by the outer edge of the head or carapace ; this ridge (d i 

 was about 15 mm. in width, and was due to the heaping up of the tine 

 sand; in section it would be low conical; one would suppose that the 

 action of the ed' r e of the head would make a furrow rather than an ele- 

 rated ridge. 



The tracks (/) were opposite, and quite regularly concavo-triangular, 

 the apex of the triangle rounded, and directed backwards, the sand being 

 pushed slightly up on the posterior edge of the track. 



The tracks of each side were directly opposite each other, and those of 

 each pair directly iu line with those of the pair in front It was notia d 

 that the distance apart of the tracks varied with tin- rapidity of the half- 

 walkuur, half-swimming movements of the animal. It was Been that the 



tracks were made by the hindermost, or sixth pair, of limbs only, no im- 



pn -ion being left in the sand by the feet in front. Tin- triangular 



shape of the traek was due to tin- spreading out of the two spatulale 



spine-, of the lasl Begmenl of the leg. It should be observed that the 

 distance apart, outside measurement, of the traek. is about two-thirds 

 that of the entire trail. 



ipressiom 1 footprints of aquatic animals and imitative markinj 



carboniferous rocks. Amer. Journ. 8c. and Arts, 3d Series, V. Jan 1873, pp. 16 24, 

 i: - i . Also Acadian Qeologj 2d edit. Supplement 1*78. 



\\V. April, 1900, p W8 



