4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. ^2 



expansion, though the incomplete surfaces makes this point sHghtly 

 uncertain. Neither can it he definitely determined whether the ischia 

 met on the median line, though I am inclined to think they did. The 

 rounded and somewhat thickened posterior border is deeply concave 

 from end to end. The sweep downward from the iliac articulation is 

 especially pronounced. On the posterior external surface at the mid- 

 length of the bone is a raised ridge with roughened surface marking 

 the point of insertion for a strong muscle. 



The form and principal features of this bone are well shown in 

 plate 2. 



Measurements ' centimeters 



Greatest length 8i 



Greatest width of proximal end 44.5 



Greatest width at lower end of pubic articulation 32 



Greatest length of pubic articular surface 37.5 



Greatest transverse diameter of articular end for ilium 10.5 



RELATIONSHIPS 



The scapula cannot be closely correlated with any of those of 

 described genera, and the ischium differs so much in its details from 

 those with which it has been compared as to indicate an animal with 

 a considerably different pelvic structure than any of the Sauropoda 

 with which we are acquainted to-day. That both of these bones 

 pertain to the same individual cannot be proven, but that both are 

 Sauropod in aspect seems certain. 



In size the scapula approaches Camarasanrns, but it differs by the 

 non-icxpansion of the upper anterior border and the very much thinner 

 blade; from Diplodocns it is to be distinguished by its larger size and 

 the direction of the spine in relation to the longitudinal axis. In the 

 present specimen this angle is approximately 90°, whereas in Diplodo- 

 cns and Aiiiphicocliis it is acute. The scapulae of Apatosanrus, 

 AmpJiicoclns, and BracJiiosaunis are more slender and with a much 

 more constricted shaft at their narrowest width. Haplocanthosauriis 

 is very much smaller and has a very different outline. 



GEOLOGICAL OCCURRENCE 

 At my request Mr. Reeside prepared the following note on the 

 stratigraphy : 



NOTE ON THE STRATIGRAPHY OF SAN JUAN COUNTY, NEW MEXICO, 



WITH ESPECIAL REFERENCE TO THE OCCURRENCE OF DINOSAURS 



The oldest rocks exposed in San Juan County, New Mexico, have been 



assigned to the McElmo formation of Jurassic or Lower Cretaceous age. The 



overlying rocks, of L^pper Cretaceous and Tertiary age, have been divided into 



