PLATE 22A. 
Chelone crassicostata. 
Portion of the carapace, half the nat. size, with the corresponding series of marginal 
plates, m6-—m12, and py. 
pl3 and pla, the third and fourth costal plates of the left side; p/5—pl8, impres- 
sions in the matrix of the succeeding costal plates. 
