658 ME. AV. H. HAEDAKER ON A FOSSIL-BEAEING HOEIZON [DeC. I912, 



These latter made contact with the ground mainly by the toes, so 

 that merely impressions of the toes and of the balls at the base of 

 the toes are displayed. 



Pootprints of amphibia and reptilia have long been known from 

 the Rothliegende of Germany. Fortunately for our present purpose, 

 many of these have been described and figured in detail by Prof. 

 W. Pabst in his great monograph — ' Die Tierfahrten in dem 

 Rotliegeuden Deutschlands,' published in 1908 (Nov. Act. Acad. 

 Caes. Leop. -Carol, vol. Ixxxix, pp. 315-481 & pis. i-xxxv). 



In the descriptions and figures of the Hamstead footprints 

 given in the present paper, I have adopted throughout the de- 

 scriptive terms and special plan of measurement originated by 

 Prof. Pabst. In the final column of each table, which I have 

 devoted to a single Hamstead type, I have inserted the corre- 

 sponding measurements from Prof. Pabst's table of that Continental 

 type of species which appears to be identical with the Hamstead 

 form, or to be its nearest ally. 



I have numbered the Hamstead types from Hi to Hg. The foot- 

 prints of types 1, 2, 3, and 4 are shorter, or at any rate not 

 markedly longer than they are broad ; whereas those numbered Hg 

 and H*^ are distinctly longer than they are broad. 



The measurements given in the tables refer to : — 



1. Length of footprint. — From the end of the longest toe to the heel. 

 2.1'Width of footprint. — From tip to tip of the outside toes. 



3. Length of toes. —The toes are numbered 1 to 5, in which 1 corresponds 



in position to the human thumb, and thus appears on the inside of 

 the track. In cases where the left and right sides of the track are not 

 both present on the specimen the shortest outside toe is regarded as 

 No. 1. 



4. 'Track-measurement' I [Pabst]. — From the centre of a fore footprint 



to the centre of the next print of the hind foot behind it. The 

 arbitrary assumjition is here made that, as in the tracks of modern 

 salamanders, the fore footprint is slightly in front of the hind foot- 

 prints which immediately followed it in time. The impression of the 

 hind foot is usually also slightly the larger of the two. 



5. 'Track-measurement' II [Pabst]. — From centre to centre of a fore 



footprint and the next hind footprint before it in the track. This 

 measurement is generally greater thaji track-measurement I. 



6. Length of stride. — The distance between two successive appearances 



of rhe same foot in the ti-ack. This is approximately equal to the sum 

 of track-measurements I & II. 



7. Width of track. — -The distance between the line of tracks made by 



the feet on the left side of the animal and that made by the feet on the 

 right side. In footprint reliefs the footprints on the right side of the 

 forward stepping track are those made by the left foot of the animal 

 and vice versa. 



Descriptions of the six Hamstead Types. 



None of these forms have been met with in the Carboniferous 

 rocks of Britain or of the Continent of Europe, but forms some- 

 what similar to Hi (Ichnium spJicErodactyJum) and H.5 {Ichnium 

 gampsodactyliuii) have been recorded from the Coal Measures of 

 America. 



