522 HrCHARD SWAXX LULL OX 



Type, no. ^, of the Hitchcock cabinet, on gniy sandstone from Turner's Falls, Massa- 

 chusetts. 



Plesiornis mirabilis E. Hitchcock. 



Plesiornis mirabilis E. Hitchcock, '65. \). 35, pi. 20. 



Possibly referable to Anchisauripus tuberosus E. Hitchcock, especiall}^ the larger 

 track, though the smaller track does not resemble it very closely. This species is based 

 upon a single specimen, no. f^, of the Hitchcock cabinet, which is peculiar not only in 

 the lack of similarity of the two sets of footprints, but also in the presence of more or 

 less parallel markings which may be due to dragging tails or limbs or to some other body 

 which may have been drawn along. 



Plesiornis giganteus C. H. Hitchcock. 

 Plesiornis giganteus C. H. Hitchcock, '89b, pp. 118, 122, 126. 

 Probably referable to Anchisauripus minusculus. 



Genus Sillimanius E. Hitchcock. (For B. Silliman.) 



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

 Ornithopus E. Hitchcock, '48, p. 191. 



Generic characters. Bipedal, tetradactylous, hallux rotated so as to be in line with 

 the fourth digit. Digitigrade to semiplantigrade. 



This genus is founded on Weathersfield shale specimens and the true characters are 

 obscured. The type species is Sillimanius tetradacti/lus E. Hitchcock. 



Sillimanius tetradactylus E. Hitchcock. 



Sillimanius tetradactylus E. Hitchcock, '45b, p. 24. 



Ornithopus gallinaceus E. Hitchcock, '48, p. 192, pi. 8, fig. 1; '58, p. 87, pi. 14, fig. 

 10; pi. 58, fig. 1. 



Sjjccific c/iaracters. Pes: divarication of digits I and II, 110° ; of 11 and III, 35°; of 

 III and IV, 45°; of II and IV, 80°. Length of digit I, .043 m.; of II, .043 m.; of III, .076 

 m.; of IV, .051 m. Length of foot impression, .097 m. Distance between lateral tips, 

 .069 m. Length of step, .178 m. Width of trackway, .064 m. Foot semiplantigrade. 



Type, no, ||, of the Hitchcock cabinet, on red shale, from Weathersfield, Connecticut. 



