FOSSIL FOOTPRINTS OF THE ,TURA-TRIAS. 521 



III and IV, 25°; of II ami IV, 45°. Length of digit I, .004 m.; of II. .217 m.; of III, 

 .285 m.; of IV, .213 m.; of the heel, .OUT m. Length of foot, .370 m. Width of the heel, 

 ,100 m. Distance between tips of the lateral toes, .105 to .222 ni. Length of step, 1.224 

 m. Width of trackway, ? .350 ni. The hallux is straight, the other digits curve inward. 

 The type specimens are nos. f|, f|, and ^, of the Hitchcock cabinet, in slightly cal- 

 careous shale, the first two from the middle of the Connecticut river at Chicopee Falls, 

 Massachusetts, the last from near Cabotville, Massachusetts. 



Genus Plesiornis E. Hitchcock. (Near a hird.) 

 Pleswrnis E. Hitchcock, '58, p. 102. 



Generic characters as given l^y Hitchcock : '' tridact^'lous, pachydactylous, hind foot 

 slightly the largest. Toes shghtly turned in towards the line of direction; terminated by 

 blunt claws, or pellets. Highly ornithoid; the tracks distinguished from those of birds 

 only by being arranged two ))y two along the median line, with a wide interval between." 

 The footprints thus described by Hitchcock under this genus are doubtless in every 

 instance those of two animals walking oue after the other, a tlieorv which Hitchcock 

 at first held, but afterwards abandoned on the ground that such tracks occurred too fre- 

 quently to be thus explained. The so called fore foot track is a typical pes impression 

 and never that of such a manus as one would expect from the very Anomoepus-like 

 appearance of the hind foot. That one animal followed another frequently is not 

 unlikely, if, as the present author believes, the animals resorted to the congregating 

 places for breeding purposes, and the slight difference in size could readily be a sexual 

 character. The quadrupedal nature of the tracks seems amply disproved. Some of the 

 species are referable to known bipedal forms, the others it will be necessary to retain 

 under the present genus, whose revised characters may be thus defined : bipedal, digiti- 

 grade, tridactyl forms, digits terminated by bhuit or pellet-like claws. Small forms of 

 doubtful affinity. 



Plesiornis pilulatus E. Hitchcock. 



Plesiornis jMidatus E. Hitchcock, '58, p. 103, pi. 17, fig. 8; pi. 30, fig. 4. 



Specific characters. Pes: divarication of digits II and 111,35°; of HI and IV, 35°; 

 of II and IV, 70°. Length of digit II, .033 m.; of HI, .053 m.; of IV, .038 m. Length 

 of foot, .053 m. Distance between lateral tips, .038 m. Length of step, .183 m. Width 

 of trackway, .050 m. 



The foot is quite similar to that of Grallator, except for the form of the claw and the 

 occasional presence of a spur-like process on the iinier side of the foot. 



