68 PROCEEDINGS OF THE AMERICAN ACADEMY. 



3 cm. long and about 9 mm. wide. It is straight and short. The 

 individual tracks are opposite each other, as in those of Limulus. The 

 animal must have leaned more to the right side, as the tracks on this 

 side are larger, deeper, and much more perfect than on the left side. 

 The most perfect ones are in shape ajraost exactly like those made by 

 Limulus when half walking and half swimming in very shoal water. 

 A typical track may be described as forming a low triangle, the apex 

 pointing backward ; it is hollow, the interior forming a hollow triangle 

 surrounded by a raised ridge. 



There are six pairs of tracks, with traces of a seventh. The width of 

 the trail is 9 mm., but probably if the entire trail were perfect on the 

 left side it would have measured about 10 mm. in width. The tracks are 

 opposite to each other. The largest and best marked individual track is 

 5-6 mm. wide and 3 mm. deep (or long) from in front to the apex or 

 hinder part. The tracks of each pair are very near to each other, and 

 those in the front part of the trail tend to be united into a simple trans- 

 verse ridge. 



There are no secondary tracks in between the others, and in this respect 

 the track differs from that of M. narragansettensis, and resembles that of 

 Limulus. 



The original of this track is in the paleontological collection of the 

 Peabody Museum of Yale University. I am indebted to the kindness of 

 Professor C. E. Beecher, the curator, who did me the favor to send me 

 an excellent cast, from which the above description has been made. 

 Professor Beecher informs me that in the beds of the Chemung group at 

 Warren, Pa., there are no remains of trilobites ; and he expressed his 

 belief that the tracks were those of some merostome. It is to be observed 

 that there is no median furrow or trail made by a tail or caudal spine, 

 and no furrow or ridge made by the edge of the body or carapace. The 

 merostome which made it most probably had no caudal spine. And yet 

 the tracks are otherwise very similar to those of Limulus. It may be 

 observed that all the Eurypterida are provided with a telsou, either broad 

 or narrow and spine-like, and their trails would evidently include a furrow 

 made by such a spine. The Limulidae were represented in the Devonian 

 by Protolimulus eriensis Williams (" associated with typical Chemung 

 fossils"). Was this track made by a young individual of this genus, 

 with the caudal spine too short to make a trail ? If not, was it made by 

 a Bunodes, which lived in the Upper Sihirian of Europe, but has not yet 

 been discovered in America, and had no caudal spine ? But Bunodes 

 vyould perhaps have left a lateral furrow made by the broad thin edge of 



