SUMMARY 383 



from the Trinity sands of Oklahoma, are Morrison, As I have stated, 

 Morosaurus is apparently represented in Europe by forms from the Mid- 

 dle Jurassic (Oxfordian) of Portugal and from the English Wealden. 

 None of the family has been recorded from Tendaguru. An allied family, 

 the Pleurocoelidae, which includes the rather primitive dinosaur Pleuro- 

 ccelus, is sparsely represented in the Morrison, more abundantly in the 

 Potomac and in the Wealden of England and Aptian of Portugal. I 

 should not consider the representatives of either of these families abroad 

 of any great stratigraphic value; so that, as these are the only genera 

 common to both Europe and North America, the Sauropoda throw little 

 light on the age of the Morrison in terms of European stratigraphy. But 

 the remaining families of Morrison Sauropoda — the long, slender Diplo- 

 docidae and the robust Brachiosaurida' — represent two extremes of spe- 

 cialization and therefore, as they are known with a high degree of com- 

 pleteness, should be of marked importance as correlating fossils. 



Tlie Diplodocida?, including the single genus Diplodocus. with its two 

 or three American species, is unknown elsewhere, unless, as the Tenda- 

 giiiu authorities believe, the family is represented in that fauna by 

 GigantoxaurHs of Fraas. At all events, tlie comparison is not sufficiently 

 close to be of more than corroborative value. Tbe last family, tlie 

 Bi'achiosauridse, or Barosaiiridiv, as perhaps it slioidd be called, in- 

 cludes tlnvc American genera — Braclilosunnis Riggs, HaplocdniJiosfdinis 

 ilatclicr, and liarosaunis ^laisli — wliich, as Doctor Matthew lias sug- 

 gested, may i)e tlie same as Bnuliiomiirus, in which case the older name, 

 BdiDsimrns. takes ju'ccedence. Of these HapJocanthosaunis is evideiitlv 

 exclusively American, but Bracliiosaurus, as I have emphasized, includes 

 not only the American, but at least two well defined Tendaguru species 

 also. The Morrison Brackiosaurus comes from a horizon which, accord- 

 ing to Riggs, contains \ari(»us species of Apatosaurus (^ Brontosaurus) 

 and Morosaurus. 



Tbe only Stegosauis tluis Far recoi-decl fi'om the ^foi-i'ison belong to 

 tbe genus Stegosnunis. with thix'e di' I'our species, and to the closelv 

 ;illied. if not identical. Diracoilon. .\s I have slioMti, Stegosaurus seems 

 to he i-e|)i-esented hy species, piohahly ancestral, from the OxCoi'dian and 

 Kimmeridgian of l*]ngland, l)nl ii|>|iai'ent ly is very ditl'd'ciit I'lMm the so- 

 called "Stegosaiirs" of Tendaguru. 



Sim .m \i;y 



The conclusions 1 would diaw tVom this |ii-eliminai'v stud\- of the 

 |ii'olilem sei-\c to emphasize the ilillicidt\ of accurate comparixin of fossil 

 rei)tiles of huge size when we lia\c only \ery iucomplete matci'ial. whicli 



