12 CHELONTIA. 
The mobility of the fore part of the sternum is extremely variable and depends on the 
amount of ossification which has taken place near the transverse suture, but no joint is 
developed, Not less variable is the width of the inguinal bridge, which is sometimes 
not even the same on either side of the same individual. With regard to coloration, 
every degree of transition occurs from a finely mottled head to one of uniform 
coloration without any spots. 
This species is so closely allied to Stawrotypus triporcatus that some difficulty exists 
in referring young examples to either of these two species. Young examples of J. 
triporcatus do not seem to possess the very broad front part of the sternum by which 
the old ones are distinguished. Therefore in maintaining for the present the genus 
Claudius, I cannot follow Cope in including in it his C. severus, but restrict it to C. 
angustatus, for which it was originally formed, although the characters assigned to it 
seem to me scarcely sufficient to justify a distinct generic appellation. 
CLAUDIUS. 
Claudius, Cope, Proc. Ac. N. Sc. Phil. 1865, p. 185. 
1, Claudius angustatus. 
Claudius angustatus, Cope, Proc. Ac. N. Sc. Phil. 1865, p. 187; 1872, p. 28; Proc. Am. Phil. 
Soc. 1869, t. 9; Dum. et Bocourt, Miss. Sc. Mex., Rept. p. 20, t. 4. 
Claudius megalocephalus, Bocourt, Ann. Sc. Nat. Zool. 1868, p. 122; Cope, Proc. Ac. N. Sc. Phil. 
1872, p. 27. 
Hab. Mexico, Tabasco (Cope). 
Called “'Talmame” by the natives. Carnivorous. 
CINOSTERNUM. 
Cinosternum, Spix, Test. et Ran. Bras. p. 17 (1824). 
Of the twelve or thirteen species known of this genus, not less than nine are peculiar to 
the Central-American fauna, one only occupying territories in the South, and two or 
three * in the North. The distinction of the species is a difficult task; and it is still 
more difficult to select distinctive characters from the lengthy descriptions by authors 
who notice the most variable details. The shape of the shell, of the individual scutes, 
of the beak, tail, the width of the hinder sternal lobe are all variable individually, as 
well as according to sex and age. In the following synopsis I have admitted such 
characters only as may be more or less fully relied upon. 
* It is not within the scope of this work to investigate the question whether Cinosternon hippocrepis of 
Gray and Platythyra flavescens of Agassiz are identical or not, as there is no evidence of either occurring within 
the limits of Mexico. 
