DESCRIPTION OF DEVONIAN TRACKS, ETC.—AMIL. 331 
The impression or track made by the left fin or spine appears 
slightly in advance of that made by the right appendage in all 
the eight pairs preserved on the type specimen, which seems to 
indicate that the creature used its appendages in locomotion in 
a slightly alternating manner, striking the mud with the left 
appendage first. The average distance in advance of the left 
imprint or track from the right is between three and four milli- 
metres measured in a direction at right angles to the course 
taken by the organism from the apices of the monticules. 
The slabs on which these tracks are preserved consists of a 
thin-bedded, fine-grained, greenish and chocolate-red coloured, 
siliceous sandstone with numerous minute glistening scales and 
particles of mica along the divisional planes of stratification. 
The following table is prepared with a view of giving the 
number of pairs of tracks preserved on the type-specimen, the 
exact measurements of the linear depressions or imprints made 
by the spine-like appendages as well as the distances between 
them, the relative size and distance between each and the 
difterent pairs of the monticules measured from their apices, 
together with the length of the stride : 
MEASUREMENTS IN MILLIMETRES TAKEN FROM TYPE-SPECIMEN. 
Greatest Greatest : 
Length of | Length of /qiameter of diameter of|, Distance 
PaIRS OF TRACKS. | left linear |right linear] the left the right |betweenthe 
depressions |depressions | »onticules.| monticules.|Monticules. 
MIPS tales. eens se 5.00 mm. | 2.50 mm. | 2.50 mm. | 1.50 mm. | 5.00 mm. 
" Second ODI revere ate 5.50 mm. | 1.50 mm. | 2.50 mm. | 1.50 mm. | 4.00 mm. 
‘IMowigel yore os eo opel 4.50 mm. | 3.25 mm. | 3.50 mm. | 1.25 mm. | 5.00 mm. 
Hourth pain ....--.- 4.25 mm. | 1.50 mm. | 2.00 mm. | 1.00 mm. | 8.00 mm. 
| Fifth [OLNR eS crcleneaeres 6.50 mm. | 4.00 mm. | 2.75 mm. | 1.00 mm. | 5.50 mm. 
Sibi aljopvien cougepoor 4.50 mm. | 3.50 mm. | 2.00 mm. | 2.00 mm. | 7.00 mm. 
| Seventh pair........ 5.00 mm. | 3.75 mm. | 2.50 mm. | 1.75 mm. | 5.50 mm. 
Biighishypadrse esse 5.00 mm. | 2.25 mm. | 2.25 mm. | 1.75 mm. | 5.50 mm. 
