14 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 80 



in length with median toes. Forefoot placed in front of hind. Feet 

 turned slightly inward toward line of movement. With or without 

 tail drag. 



Genotype. — Nanopus caiidatus Marsh. 



KEY TO SPECIES 



Small size. Toes stout with obtusely rounded ends. Lateral toes of pes 

 shorter than median toes. 



N. caudatus Marsh 

 Small size. Toes slender, with acutely pointed ends. Lateral toes of pes 

 shorter than median toes. 



N. merriami Gilmore 

 Large size. Toes slender, acutely pointed. Lateral toes of pes subequal 

 in length with median toes. 



N. maximus n. sp. 



Fig. 



3. — Tracks of Nanopus obtusis Matthew. la, hindfoot: 

 lb, forefoot. Natural size. (After Matthew.) 



Fig. 4. — Tracks of A^anopus quadratns Matthew. la. hindfoot ; 

 id, forefoot. Natural size. (After Matthew.) 



The two species N. obtusis and A^. quadratns from the Coal Mea- 

 sures of Nova Scotia referred to this genus by Matthew show such a 

 radically different foot plan as to indicate that their affinities lie else- 

 where than in the genus Nanopus. Reference is made to the divergent 

 fifth or outer toe, the progressive shortening of the digits inward, 

 and the placing of the hindfoot in advance of the forefoot impression. 



