188 AN ATTEMPT TO DE5CR1BE THE ANIMALS THAT MADE 



0.7 inch. Length of the foot, 0.9 inch ; of the step, 3.2 inches ; 

 of tlie middle toe beyond the others, 0.35 inch. Distance between 

 the tips of the lateral toes, 1 to 1.2 inch; between the inner and 

 middle toes, 0.6 to 0.7 inch ; between the outer and middle toes, 

 0.6 to 0.7 inch. Angle between the axis of the foot and the line 

 of direction, lO"". Track shown, of the natural size, on Plate 6, 

 fig. 6. 



Locality. — Wethersfield, at the Cove ; on red shale. 



Remarks. — Since the discovery of the Macropterna rhyncho- 

 sauroidea, I have been in considerable doubt whether the above 

 species should not be referred to it. Certainly the two have been 

 confounded. But I have a few specimens of the Argozoum mini- 

 mum quite distinct, which, as yet, I cannot regard as a Macropter- 

 na, and therefore shall let this species remain for the present. 



Genus V. PLATYPTERNA. 



Heel very broad, as well as the foot at the roots of the toes. 

 Toes slender ; for the most part curved. Feet plantigrade. 



Remarks. — This elegant genus is distinguished by the unusual 

 breadth of the posterior part of the foot, including the heel ; and 

 yet, on many specimens of its tracks, there is no appearance of a 

 heel. It is wanting, also, in the curved or angular space between 

 the toes and the heel which belongs to the genus Steropezoum. 

 In most of the specimens, the impression of the heel is rounded 

 posteriorly ; but in the P. tenuis the heel disappears so gradually, 

 by an upward slope of the foot, that its exact termination on the 

 stone is marked with difficulty. The first species may be only the 

 Ornithopus gallinaceus, wanting in the hind toe, and were not 

 some of my specimens of 0. gallinaceus deeply impressed upon the 

 stone, I should be led to conclude them identical. 



