FOSSIL FOOTPRINTS OF THE JURA-TRIAS. 517 



the mud in the present instance would readily produce the latter, though no real clue to 

 its identity with any other genus is shown. 



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

 Massachusetts. 



? Platypterna gracillima E. Hitchcock. 

 Platiipterna gracillima E. Hitchcock, '58, p. 86, pi. 14, fig. 12. 



Specific characters. Pes: divarication of digits II and III, 20°; of III and IV, 50°; 

 of II and IV, 70°. Length of digit II, .025 m.; of III, .038 ra.; of IV, .032 m. Distance 

 between lateral tips, .036 m. Length of step, .127 to .140 m. Width of trackway, .076 

 m. Foot digitigrade, outer toes curved inward. 



This track is like that of a miniature of Argoides redfieldianm, which is probably to 

 be identified with Euhrontes dwaricatus. The foot approximates most nearly that of 

 Grallator gracilis; but the angles of divarication are far greater in the present form. 

 The species is evidently not of the genus Platypterna but is left therein provisionally 

 until further light is had upon its affinities. 



The type is no. ^, of the Hitchcock cabinet, from Turner's Falls, Massachusetts. 



Platypterna tenuis E. Hitchcock. 

 Platypterna tenuis E. Hitchcock '45b, p. 25; '58, p. 84, pi. 14, fig. 5; pi. 58, fig. 10. 



Specific characters. Pes : divarication of digits II and HI, 20° to 30° ; of III and I V^ 

 25° to 30° ; of II and IV, 45° to 00°. Length of digit II, .025 m.; of III, .042 m.; of IV, 

 .035 m. Breadth of heel, .015 m. Distance between lateral tips, .048 m. Length of 

 foot, .069 m. Length of step, .178 m. Width of trackway, .050 m. 



The form is semiplantigrade so that the whole foot does not impress ; a long Umbed, 

 delicate type. 



The type specimen is no. };, of the Hitchcock cabinet, on red shale from Weathers- 

 field, Connecticut. 



Platypterna delicatula (E. Hitchcock). 



Calopm delicatidus E. Hitchcock, '45b, p. 25. 



Pkdypterna delicatida E. Hitchcock, '58, p. 84, pi. 14, fig. 6 ; pi. 58, fig. 8. 



Specific characters. Pes: divarication of digits II and III, 22°; of HI and IV, 18°; 

 of II and IV, 40°. Length of digit II, .017 m.; of HI, .028 m.; of IV, .010 m.; of the 

 heel, .010 m. Widtli of heel, .008 m. Distance between lateral tips, .015 m. Length of 

 step, .076 m. Width of trackway, .050 m. 



