MORPHOLOGICAL REVISION OF THE SUBORDER. 133 



The centra hav'e the usual elongate form of this portion of the column; the 

 dorsals have the last traces of a keel, so the bottom line of the centrum is straight, but 

 the lumbars have no keel, and the 1)ottom line is concave. The transverse processes 

 are all lost, but they originated high up on the side of the centrum and the neural 

 arch. The intercentra have the characteristic form of the species and the rib-head 

 articulated in the triangle between the upper portions of the centra and the end of the 

 intercentra. Several rib-heads are preserved in this position. 



The lumbars are distinguished by the presence of the capitular facet on the side 

 of the anterior articular edge. Between the last dorsal and the first centrum with a 

 well-developed capitular face there is one with a somewhat imperfect face. The heads 

 of several ribs are preserved in position in the lumbar series, showing that they touched 

 the end of the intercentmm in the first lumbars as well as the capitular face on the 

 edge of the centrum. 



The spines are very characteristic in appearance. The bases of the dorsal spines 

 are somewhat longer antero-posteriorly than transversely, but a few centimeters from 

 the base a notable swelling gives the spine a quadrangular section. The sides of this 

 swelling are marked by ridges and grooves, giving it a roughly fluted appearance. 

 Above this the spine becomes rounded and then oval (see fig. 14). A deep groove on 

 the posterior face persists nearly to the summit, while a similar one on the anterior 

 face disappears at about half the height of the spine. The apices of the spines are 

 very slender ; in those most nearly complete they are not over 2 or 3 mm. in width. 



In the lumbars the bases of the spines are much more elongate antero-posteriorly. 

 They do not swell to quadrangular shape, but pass directly to a rounded section, 

 though there is a short region marked by rugose ridges in the position of the swelling. 

 In one of the posterior lumbars the spine is complete and shows that the tip end was 

 slightly enlarged and roughened. 



Measurements. 

 Nos. 4054 and 4055 American Museum. 



Tiiin. mm. 



Length, bottom line of centrum 27 Height of spine above neural canal 64 



No. 4012 American Museum. 



mm. mm. 

 Length, bottom line of — Length, bottom line of — ■ 



An anterior dorsal 18 5th presacral 19 



I2th presacral (probably the i6th vertebra) 24 4th " 16 



nth " 24 3d " 16 



loth " 24 2d " 13 



9th " 23 1st " 12 



8th " 23 1st sacral 26 



7th " 22 2d " 24 



6th " 20 3d " 22.5 



No. 1019 University of Chicago. 



mm. mm. 



Length, bottom line of a lumbar 32 Dorsals, continued: 



Anterior face : Anterior face : 



,,.,.. , Horizontal diameter 27 



Horizontal diameter 26 Vertical diameter 33 



Vertical diameter 29 Transverse diameter, base of spine 19 



Transverse diameter of centrum at middle 14 Antero-posterior diameter base of spine... 14 



Vertical diameter of centrum just posterior to Transverse diameter, 5 cm. above base 18.5 



^fch 22 Antero-posterior diameter, 5 cm. above 



Posterior face, vertical diameter 29.5 base 17 



Length, bottom line of posterior dorsals and Length of incomplete dorsal spine of same 



four lumbars, each 31 vertebra, probably 100 mm. short 873 



Dorsals: Length of second incomplete dorsal spine. 800 



Length, bottom hne 28 Length, complete lumbar spine 675 



