32 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 



// 



Type locality. — Hermit Trail, Hermit Basin, Grand Canyon Na- 

 tional Park, Arizona. 



Geological occurrence. — Coconino sandstone (a loose slab from 

 hillside at a point about 125 feet above the base), Permian. 



The trail here described consists of two parallel lines of tracks 

 between which the drag of a caudal appendage is clearly registered. 

 The lateral lines are formed by clusters of three imprints, evidently 

 made by tridactyl, pointed extremities, the longer axis of which 

 stands at about 45 degrees to the line of direction. The clusters al- 



FiG. 20. — Palcohclcura tridactyla. Type, No. 11.145, U. S N. M. 

 Diagram of trackway. Arrow indicates line of movement. 

 ^ natural size. 



ternate on the two sides. This alternating movement of the limbs of 

 opposite sides is indicated in the undulating movement of the tail 

 drag, which is quite clearly shown in plate 12, figure i. The direc- 

 tion of movement is indicated by the drag of the toes as being in 

 the direction shown by the arrow (fig. 20). The inner toe seems 

 to be the smallest ; the outer two are subequal in size. The greatest 

 width of the trackway is 22 millimeters, length of stride about 17 

 millimeters, distance between single imprints of each cluster about 

 3 millimeters, and width of each cluster of three about 8.5 milli- 

 meters. 



