FOSSIL FOOTPRINTS OF THE JURA-TRIAS. 543 



Typopus abnormis E. Hitchcock. 

 7)/jj()jj>is abiionnis E. Hitchcock, '45b, p. 25; '58, p- 105, pi. 17, fig. 9; pi. 45, fig. 7. 



This form is much larger thau the following species. 



Type specimens, nos. -\- and ^, of the Hitchcock cabinet, from Turner's Falls, Massa- 

 chusetts. 



Typopus gracilis E. Hitchcock. 



TyjJopus gracilis E. Hitchcock, '58, p. Ul6, pi. 17, fig. 1(1. 



Founded upon a single track and its counterpart on the red shale of Weathersfield, 

 Connecticut ; nos. ^ and f| of the Hitchcock cabinet. 



COKCLUSIONS. 



The creatures, the record of whose existence has remained impressed upon the 

 ancient shales and sandstones, may be divided into two groups in accordance with their 

 mode of progression : those of bipedal and those of quadrupedal gait. The former, it 

 may be safely assumed, are. in all probability, dinosaurs, for aside from man, many birds, 

 and some modern lizards, they are the only vertebrates whose gait when erect could have 

 been a true walk or run with alternating steps, which without exception, the bipedal 

 tracks show, there being no instance of the record of a jumping form. The presence of 

 birds in the new red sandstone has not been proven, lizard.s are never hahituaJ bipeds, 

 man is clearly out of the question, hence by elimination we narrow the possible origin of 

 such tracks down to the dinosaurian forms. This conclusion is strengthened by the pres- 

 ence of the fossil bones of the Anrhindiiridiie, a family of primitive carnivorous dinosaurs 

 having affinities with the Megalosauria. 



The most abundant <)i the tracks are attributable to members of that family, creatures 

 ranging in size from about seven to fourteen feet, so trul\ liipedal that the manus and 

 tail never impress. The pes is tetradactvl but only exceptionally does the claw of the 

 strong grasping hallux leave a mark. The claws are rather pointed and the whole foot is 

 very bird-like. These footprints form a natm-al group to which the generic name of 

 Ancliisauripus is given and which corresponds to the family Aiicliiaannchte. 



Allied to Ancliisauripus is another carnivorous form whose foot is more specialized 

 than that of the t'ormei- in the enfeeblement of the hallux and increase of weight which 

 has rendered the foot Hatter and its pads more complex. This creature, Gigandipus, 

 reminds one strongly ot the Jurassic Allosaurus though in the latter the claws were 

 probably more trenchant and the wliole foot more efficient as a grasping organ, (iigandi- 

 pus, known from but one specimen, shows a sinuous caudal trace. The dragging of the 



