162 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 83 



parison. Of the two hadrosaurian genera now known from this 

 formation, Kritosauo'us may be dismissed from consideration, as the 

 spines on the anterior caudals of a larger individual (Parks, 1929) 

 do not have the elongated proportions of Parasaurolophiis. The 

 only other possible assignment, so far as known at the present time, 

 is that this tail might pertain to the genus Hypacrosaurus^ but more 

 diagnostic materials are required to establish such a suggestion, 

 furthermore, Hypacrosaw^s is an Edmonton genus, although since 

 it has been recognized in the Two Medicine formation of Montana, 

 no good reason exists why it might not also be found to occur in 

 the Kirtland formation. 



The tail shown in plate 13. figure 1, was found articulated and is 

 complete except for the possible loss of a vertebra or two at the 

 distal termination. There are 68 caudal vertebrae present. These 

 were in series with the posterior sacrals of which there are three 

 centra preserved. The posterior end of the left ilium was retained 

 in articulated position, as shown in plate 13, figure 1. All the verte- 

 brae posterior to its hinder border are regarded as caudals. The 

 spinous processes are largely missing on the first six caudals, and 

 the chevrons on all anterior to the tenth. The first complete spine 

 found on the eighth vertebra has a length of 481 mm (about 19 

 inches). The ninth is 479 mm, and as they become progressively 

 shorter in a posterior direction, the presumption is that the missing 

 anterior spines would progressively increase in length. Based on 

 the progressive rate of change in the known spines it would be a con- 

 servative estimate that the first caudal spine Avould have a height of 

 51G mm (about 201/4 inches). 



Parks gives the length of spines in the first four vertebrae of 

 the type of Parasaurolophus walkcri as 415, 410, 400, and 390 mm, 

 respectivel}^ Thus the Kirtland specimen exceeds P. w^dkeri in 

 spine development, although the femur of the latter is slightly longer, 

 measuring 1,032 mm, as compared with 985 mm for the specimen 

 under consideration. 



The gTeat dorsoventral depth of the tail is strikingly illustrated 

 by a vertical measurement taken across the fourteenth vertebra. 

 From spine top to chevron tip it measures 311/2 inches. The seventh 

 caudal has a spine 375 mm and a centrum 69 mm long; the tenth 

 vertebral centrum is 65 mm long. 



There are transverse processes on the first 16 vertebrae, but these 

 are so poorly preserved as to be unworthy of description. As the 

 principal features of this series are clearly set forth in plate 13, 

 figure 1, further description of the tail is imnecessary. 



The posterior half of a right maxillary, partly filled with teeth, 

 was found in the block carrying the sacral portion, and it is pre- 



