484 



RICHARD SWANN LFLL ON 



Batrachopus gracilis (K, Tliiclionck). 



Anisopus gracilis E. Hitchcock, '48, p. 22S, pi. I(i, fig. .3-4; '58, p. fil. pi. 0, fig. 4; 

 pi. 35, fig. 5; pi. 36, fig. 1-5; pi. 58, fig. 9. 



Anisichnus gracilis C. H. Hitchcock, '89b. p. 119. 



Specific characters. Pes : divarication of digits I and H, 23° ; of 

 II and III, 20°; of III and IV, 30° ; of I and IV, 73°. Length of digit 

 I, .011 m.; of II, .021 m.; of III, .023 m.; of IV, .031 m. Length of 

 foot, .036 m. Distance between lateral tips, .028 m. All of the digits 

 are clawed. The variation of the figured specimen, no. ,-^, from 

 Hitchcock's described type is mainly in the divarication, never a con- 

 stant factor. 



Manns: divarication of digits 1 and 11, 23°; of II and 111, 25°; 

 of 111 and IV, 44°; of IV and V, 62°. Length of digit 11, .012 m.; of 

 111, .013 m.; of IV, .011 m.; of V, .004 m. The poUex rarely impresses 

 and often the fifth digit is obscure gi\dng practically a functionallv 

 tridactyl track. There seems to l)e a wide range of variation in divaii- 

 cation in the manus as well. Length of step, .209 m. Manns placed 

 just in advance of the pes. 



This form is smaller than either of the preceding species (fig. 3) . 



The type specimen is no. ^, of the Hitchcock cabinet, on a slab 

 of dark shale whose locality is unrecorded. The species is reported 

 from Massachusetts, Connecticut, New Jersey, and Pennsylvania. 



Batrachopus gracilior (E. Hitchcock). 



Anisojms graclHor E. Hitchcock, '63a, p- 54 ; '65, p. 6, pi. 1, fig. 3. 

 Anisichmis gracilior C. H. Hitchcock, '89b, p. 119. 



Specific characters. Pes: divarication of digits 1 and II, 14'; of 



II and 111, ir; of 111 and IV, 15.5°. Length of digit I, to center of 

 heel, .909 m.; of II, .0125 m.; of 111, .014 m.; of IV, .015 m. Length 

 of foot, .015 m. Distance between lateral tips, .012 m. 



Manus: divarication of digits 1 and II, 35°; of II and III, 37°; of 



III and IV, 11°; of IV and V, 77°. Length of digit I, from center of 

 the rear of the track, .005 m.; of II, .008 m.; of III, .008 m.; of 



IV, .007 m.; of V^ .005 m. Length of foot, .008 m. Length of step, .94(3 m. Width 

 of trackway, .05 m. Ratio of foot to stride, as one to three. 



Fig. 3. Batrnrhopns 

 gracilis E. Hitchcock. 

 Successive tracks of 

 right and left manus 

 and pes, showing the 

 relative length of step 

 to foot impression, x 

 J. From the type spec- 

 imen, no. •'/, of the 

 Hitchcock cabinet. 



