364 University of Kansas Geological Survey. 



Carapace. 



The carapace must have been originally nearly complete, but 

 much has been lost and other portions have been injured in re- 

 moving the hard matrix. It was evidently narrow in propor- 

 tion to its length, and was pointed posteriorly. The bone 

 everywhere is very thin — from two to three millimeters in thick- 

 ness — and shows numerous small or minute pits ; no other evi- 

 dence of shields, however, is present. The sutures in some 

 places between the pleuraliaand neuralia are distinct, but for the 

 greater part obliterated. The lateral plate corresponding to the 

 third presacral vertebra has a length of 135 mm., but the very 

 thin end is wanting, and may have been prolonged to the mar- 

 ginal. Its width proximally is forty, toward the outer part five 

 or six millimeters more. The neural for this vertebra has its 

 front and lateral sutures distinct ; at its broadest part behind it 

 measures thirty-two mm. in width. 



The dorsal vertebrae are stout and cylindrical, with moderate 

 expansions at the extremities. The rib processes are stout, 

 situated near the anterior part of each vertebra, and the ribs 

 articulated with one centrum alone in the posterior vertebra at 

 least. The processes and heads of the ribs are stout, and are 

 united by a free suture. The ribs of the three presacral verte- 

 brae exposed are directed very obliquely upward ; the transverse 

 processes of the sacrum are nearly horizontal, slender, and the 

 first pair directed a little obliquely backward. 



Length of second sacral vertebra 21 mm. 



Length of first sacral vertebra 24 



Width through the articular surfaces for the transverse processes 31 



Width of transverse process at base 17 



Width of transverse process distally 11 



Length of transverse process 45 



Length of first presacral vertebra 29 



Width of centrum anteriorly 22 



Width through rib processes 25 



Length of second presacral vertebra 40 



Width of centrum anteriorly 24 



Width through rib processes 29 



Distance between inferior margin of same vertebra and the top of the 



carapace 40 



