NO. 1519. MO ROSA UR US A GILLS REDESCBIBED— GILMORE. 163 



OCCURRENCE AND RELATIONSHIPS. 



Of the tive species Mar.sh has proposed under this genus, two {M. 

 grandis" and 2L agilis) were lirst known from the Jurassic of Colo- 

 rado. The other forms {M. itiipar, rohusUis^ and hntus)^ as well as 

 M. grandis^ have been found in the Jurassic of W3^oming. If Hatch- 

 ers suggestion proves correct — that the beds at Canon Cit.}', Colorado 

 (from which Marsh obtained some of his type specimens), are the equiv- 

 alent of the marine or Baptanodon beds of northern localities, and there- 

 fore represent a lower horizon of the Jurassic — it would be to this 

 region that we would naturally turn for the ancestors of those species 

 found in the higher beds of the Wyoming localities. 



The small size, in addition to the presence of a second intercentrum 

 on the axis and no evidence of bifurcation of the single spine of the 

 third cervical of M. agilk, might suggest a somewhat primitive con- 

 dition as compared with the later forms. This supposition, however, 

 bears but little weight and is not substantiated bv other paleontological 

 evidence, as several genera and species of the Opisthocoelia, apparently 

 identical, have been found in l)oth regions, and it is quite probable 

 that later we shall find that 3£. agllis enjo3^s a like geological and geo- 

 graphical distribution. Already Professor Osborn* has referred to a 

 forefoot from the " Bone Cabin " quarry as possibly ])eing J/, agiJis, 

 but this is doubly doubtful since we are uncertain of the identification 

 of the so-called forefoot of M. a gills hj Marsh. Of the five species 

 named by Marsh but few distinguishing characters have been given, 

 and at this time little can be said regarding the relationship of the 

 several forms. 



The primitive characters found in Morosauriis: agills suggest to the 

 writer the possibility that the tjpe specimen, when more complete 

 material is known, may be found to pertain to one of the members of 

 the more primitive family Brachiosauridtv,'' possibly the smaller genus 

 IlapJoeaiit/iosaiu'iis^' Unfortunatel}", none of the representatives of 

 this family have the anterior cervical region preserved; so judgment 

 on the question raised here must be deferred until homologous parts 

 are discovered. While the writer is aware of the close relationship 

 of the Brachiosaurida? and Morosauridtv. the simple spine of the 

 third cervical of Morosawnis agllis is particularly suggestive as to the 

 possibility of its being a member of the former family. 



«Williston has pointed out that M. impar and grandis are synonyms (Kans. Ubiv. 

 Quart., VII, p. 173). 



6H. F. Osborn, Bull. Am. Mus. Nat. History, III, 1899, p. 170. 



<^E. S. Riggs, Field Columbian Museum Publication, p. 94, Geol. Ser., II, No. 6, 

 Sept. 1, 1904. 



f' J. B. Hatoher, Memoirs of Carnegie Museum, Pittsl)urg, II, No. 1, 190.'>. 



