518 RICHARD SWANN LULL ON 



This is the smallest representative of the genus. 



Type specimen, no. {-\, in the Hitchcock cabinet, on red shale from Weathersfield, 

 Connecticut. 



Platypterna recta (E. Hitchcock). 



Hdvpedactylus rectus E. Hitchcock, '48. p. 209, pi. 5, fig. 5 ; pi. 24, fig. 7. 

 Phdiipterna recta E. Hitchcock, '58, p. 84, pi. 14, fig. 7; pi. 47, fig. 3. 



Sjjeclfic characters. Pes: divarication of digits II and HI, 10° ; of HI and IV, 27°; 

 of 11 and IV, 36°. Length of digit II, .055 m.; of HI, .080 m.; of IV, .060 m. Distance 

 between the lateral tips, .063 m. Length of track, .095 m. Width of heel, .045 m. 

 Length of step, .140 m. Width of trackway, .140 m. 



In this form, as in I\ tenuis, the foot is semiplantigrade so that the entire foot does 

 not impress. The toes are straight but the short step and wide trackway indicate a very 

 short limbed, wide bodied form as in the case of P. concamerata. 



The type is no. I, of the Hitchcock cabinet, on hard argillaceous sandstone, from 

 Gill, Massachusetts. 



Genus Argoides E. Hitchcock. (Cyclops-like.) 



Argoides E. Hitchcock, '45b, p. 24. 

 Arrjcjzoum E. Hitchcock, '58, p. 81. 



Generic characters. Bipedal, leptodactylous, tridactylous: Toes curved, the latter 

 ones more or less outward and upward behind, so as to be keel shaped. Digitigrade, 

 rarely showing a heel. 



Argoides isodactyletus (E. Hitchcock). 



Argoides isodactyletus E. Hitchcock, '45b, p. 24. 

 Argoides minimus E. Hitchcock, '45b, p. 24. 



Argozoum 2'>(i'>'idigitatum E. Hitchcock, '58, p. 82, pi. 14, fig. 3-; pi. 35, fig. 4; pi. 

 39, fig. 1. 



Plesiornls aequcdipes E. Hitchcock, '58, p. 104. 



Sjyecific characters. Pes: divarication of digits 11 and HI, 40° to 50°; of III and 

 IV, 40° to 50°; of II and IV, 80° to 100°. Length of digit II, .023 m.; of HI, .033 m.; 

 of IV, .025 in. Distance between tlie lateral tips, .027 m. Length of foot, .030 m.; 

 of the step, .1 52 m. Width of trackway, .043 m. 



The size coupled with the extreme length of liml) in this form, strongly suggests the 



