196 Systematic Paleontology 



neural arch on the forward half. There are prominent facets for the 

 chevron bones at the posterior margin, the anterior ones being less 

 marked, as shown in pi. xvi, fig. 2. 



DIMENSIONS 



Length 41.5 mm. 



Breadth 40.0 mm. 



Depth 38.0 mm. 



The neural spine bearing the post-zygapophyses of about the tenth 

 caudal is present. It is stout, compressed and elongated fore and aft at 

 the summit. The zygapophyses are about 30° out of the perpendicular. 

 This bone fragment (No. 5650, U. S. JSTational Museum) measures as 

 follows : 



Height about 50.0 mm. 



Transverse diameter at summit 15.8 mm. 



Longitudinal diameter at summit 33.8 mm. 



A posterior caudal (No. 5372, U. S. JSTational Museum) (pi. xvi, fig. 4) 

 has the neural arch complete, except the tips of the pre-zygapophyses. It 

 resembles the one just described, except that it is relatively much more 

 slender and shows no trace of facets for the chevron bones. The spine 

 is compressed to a sharp, straight edge, and the articular faces of the 

 centrum are nearly plane. 



Length 27.0 mm. 



Depth of centrum 19.5 mm. 



Height over all 31.0 mm. 



Breadth 20.0 mm. 



Appendicular Skeleton. — Of the shoulder girdle, the coracoid is known 

 from two specimens besides which the summit of a scapula only has been 

 recognized. Of the coracoids the more complete one is No. 2523, G. C. 

 It seems, however, to have belonged to a larger individual than the 

 average size of the bones would indicate. The imperfect one is more 

 nearly of the general size. It resembles very closely that of Morosaurus 

 lentus, except for the form of the glenoid face, which, in Pleurocoelus, 

 is broader below and forms a ridge on the outer face, which is sharply 

 elevated above the general level of the bone. The portion containing the 



