TAB. XVIII. 



Trionyx incrassatus. 



Fig. 



1. Upper or outside view of the fore part of the carapace with the nuchal plate, 



half nat. size. 

 ch. The nuchal plate. 

 s\. The first neural plate. 

 S2. The second neural plate. 

 ph—ph. The three anterior costal plates of the left side. 



2. Under or inside view of the same specimen. 



ch. The nuchal plate. 



s\. The first neural plate connate with the neural spine of the second dorsal 



vertebra, of which part of the under surface of the centrum is here preserved 



and shown. 

 S2. The second neural plate, with the connate neural arch of the third dorsal 



vertebra. 

 ph—ph. The three anterior costal plates of the right side. 

 c\. The place of attachment of the outer end of the first dorsal rib. 

 c2. The portion of the second dorsal rib that becomes connate with the first 



costal plate. C2. The extremity of the rib that again becomes free, 

 es. The third rib attached to the second costal plate. 

 C4. The fourth rib attached to the third costal plate. 



