PACKARD. — PALEOZOIC ARTHROPOD TRAILS. 67 



The four narrow furrows (/) intersecting the tracks were made by the 

 lateral abdominal spines, which are bent down and trail in the mud or 

 sand when the animal is walking or moving over the bottom. The large, 

 deep, median furrow (e) was made by the caudal spine ; it was continuous, 

 uninterrupted, during the continuous forward movements of the animal. 



Another trail is represented by Fig. 2. It will be seen that it pre- 

 sents no resemblance to the other. Unfortunately I did not make any 

 notes as to the relations of the animal to the bottom. So far as I can 

 remember it was a smaller individual, and probably it moved rapidly. 

 The indentations on the margin of the trail were evidently made by the 

 feet, while the series of median furrows were made by strokes of the 

 caudal spine. The trail was 3.50 cm. wide. 



The tracks of living terrestrial Isopod Crustaceans. — Fig. 3. In this 

 connection it was interesting to ascertain the nature of the tracks made 

 by Crustacea so much like trilobites in general shape as our 

 terrestrial Isopods. One of our common Armadillo was cap- • . 



tured, its feet inked, and it was then set free and allowed to 

 " make tracks " on a sheet of paper. It will be remembered , \ 

 that the Isopods have seven pairs of ambulatory legs, the . . 

 extremities of which end in a single sharp point. The width 

 of the body is from 4 to 5 mm. It was noticed that the 

 crustacean in running put down the feet of each pair at the , , 



same time, and that the legs, and especially the pointed ex- • \ 



tremities, were perpendicular to the surface over which it 

 ran. • 



The trail thus made was a very simple one, being a double • • 



row of slightly elongated dots, the individual tracks of each 

 pair being exactly opposite to each other, as seen in the figure. • • 



When the feet dragged the dots became lines. The trail is y IGUKE 3. 

 also nearly of the same width as the body itself, though a 

 little narrower rather than wider. 



A specimen of our common Porcellio scaber was also compelled to 

 undergo similar treatment and like evolutions with the same result. The 

 trail differed in no essential respects from that of the other Isopod. 



It will be of much interest to experiment with macrurous and brachyu- 

 rous Crustacea, in order that the results may throw light on the numerous 

 tracks in the Triassic beds of the Connecticut Valley described by Hitch- 

 cock in his " Ichnology." 



Merostomichnites beecheri n. sp. Fig 4. This trail is in a fine shaly 

 sandstone of the Chemung beds at Warren, Pa. It covers an area 



