20 G. R. Wieland — Protostegan Plastron. 



The Hypoplastron. 



Greatest length inclusive of spines-.. 1*00 



Greatest width inclusive of spines 1'00±: 



Greatest length exclusive of the posterior extension ._ *65 



Greatest width exclusive of spines _ *65 



Greatest thickness . -04 1 



Length of interior spines -15 — *25 



Length of exterior spines •] — -20 



The Jtiphiplastron. 



Greatest length -50 



Greatest width _ __ -17 



Greatest thickness -036 



Thickness near terminus __ -025 



The Plastron. 



Total width across the hyoplastron 2-00-1- 



Total width across the hypoplastron 1-86 



Total length 2-00 + 



The Nuchal. 



Greatest lateral width *64 



Antero-posterior length __ *25 



Elevation of articulating surface for the last cervical 



vertebra _ __ "02 



Greatest thickness including the process for the cer- 

 vical -035 



Width of alse _ , '09 



Thickness of ala3 ..- -01— -015 



Chester, Pa., Dec. 11, 1897. 



