Note 25 — THE PLACOID BRAIN. EMBRYONIC CHARACTERISTICS NOT NECESSARILY OF A LOW ORDER.
Reading edition
The Silurian Placoids are most adequately represented by the Cestracion of the southern hemisphere; but I know not that of the peculiar character and instincts of this interesting Placoid,—the last of its race,—there is any thing known. For its form and general appearance see fig. 49, page 177.