246 AN ATTEMPT TO DESCRIBE THE ANIMALS THAT MADE 



Species 1. Herpystezoum Marshii. (PI. XVII. Fig. 1.) 

 Groove made by the progression of the animal, 0.2 inch wide. 

 Shown, of the natural size, on Plate 17, fig. 1. Plate 23, fig. 

 4, shows another specimen, from Mr. Marsh's collection, greatly 

 reduced. 



Remarks. — This species was discovered at Turner's Falls, by 

 Mr. Dexter Marsh, who, by indefatigable industry and tact, has 

 obtained a very rich and valuable collection of the footmarks and 

 other fossils of the Connecticut valley. Hence I have attached his 

 name to this animal. This paper will testify, also, that he has dis- 

 covered several other species described in it. 



Species 2. Herpystezoum minutum. (PL XVII. Fig. 2.) 



Width of the groove made by the progression of the animal, 

 0.05 inch. Shown, of the natural size, on Plate 17, fig. 2. 



Remarks. — The only difference between the two species of this 

 genus consists in size, — that is, so far as we can judge from their 

 track-way. Yet this difference is so great, that they must have 

 been produced by different species. Both of them occur at Tur- 

 ner's Falls, on reddish shale. 



Affinities of the Group. — The resemblance between the track- 

 ways of these animals and those of certain annelids, especially the 

 common earthworm, upon mud, is very striking. That such was 

 the origin of the figure 1, PI. 17, I have little doubt. Fig. 2 is 

 rather larger than the earthworm produces, and it might have been 

 made by a small mollusc. I more incline, however, to refer it to 

 the Annelata. 



