768 THE AMERICAN NATURALIST. 
presumption of its having belonged to 7. agasszziz. For we 
have already noticed that the shield in the latter species is with- 
out deep lateral incisions and has no triangular projection in 
front ; and moreover its form (see Fig. 4) agrees with New- 
berry’s statement that “the dorso-median shield is rounded in 
outline, about two feet in diameter, much thinner than that of 
Dinichthys, and with a long and relatively slender process, 
which reaches backward and downward apparently to gain 
the support of the neural spines.” ! The large size of this 
particular specimen is, however, remarkable. 
1 Loc. cit. (1889), p. 130. 
