FOSSIL FOOTPRINTS OF THE JURA-TRIAS. 585 



Specific, characters. Pes: divarication of lateral digits, 100° to 130°. Length of 

 dio-it I, .003 m.; of IL .0065 m.; of III, .008 m.; of IV, .0045 m. Very delicate claws 

 sometimes impress. Length of step. .028 to .050 m. Width of trackway, .038 m. 



Manus: one short hind toe and four front ones, the latter with a divarication of 

 138°. Digits vary in length from .004 to .005 m. Nearly straight. 



Type specimen, no. ^, of the Hitchcock cabinet, from Gill, Massachusetts. 



Genus Orthodactylus E. Hitchcock. (Straight toed.) 

 Orthodactybis E. Hitchcock, '58, p. 113. 



Generic characters. Quadrupedal, digitigrade. Pes with four long, straight digits, 

 diverging but little ; clawless and without phalangeal pads. Manus pentadactyl, digits 

 ranging through 180° or more of divarication. Impression just in advance of that of the 



pes. 



Hitchcock classes these forms with the lizards but then true position seems 

 extremely doubtful as the data which they furnish is so meager. 



Orthodactylus floriferus E. Hitchcock. 



Orthodactylus floriferus E. Hitchcock, '58, p. 114, pi. 20, fig. 7 ; pi. 45, fig. 2. 



Specific characters. Pes : divarication of digits I and II, 12.5° ; of II and HI, 4° ; 

 of HI and IV, 9.5° ; of 1 and IV, 25°. Length of digit I, .015 m.; of II, .020 m.; of HI, 

 .030 m.; of IV, .018 m. Distance between lateral tips, .013 m. Axis of foot turned 

 outward 35° to 40°. Length of step, about .180 m. Width of trackway, .182 m. 



Manus: with subequal digits about .013 m. in length, ranging through 180°. 



Type specimen, no. -f , of the Hitchcock cabinet, from Turner's Falls, Massachusetts. 



Orthodactylus introvergens E. Hitchcock. 

 Orthodactylus introveryens E. Hitchcock, '58, p. 114, pi. 20, fig. 8; pi. 51, fig. 1. 



Specific characters. Pes : divarication of lateral toes, rarely more than 20°. Digits 

 straight, very namnv, from .020 to .032 m. in length. Length of foot, .039 m. Distance 

 between lateral tips, .025 m. Length of step, .054 m. Width of trackway, .083 m. 



Manus: digits somewhat curved, about half the length of the pes. The axis of l)oth 

 manus and pes turn in toward the median line, a fact which constitutes the main point of 

 difference between this and the preceding species, in which the reverse is true. 



The type specimen is no. ^|, of the Hitchcock cabinet, on red shale from Turner's 

 Falls, Massachusetts. 



