Note 3891 — BOOK V. AN ACCOUNT OF COUNTRIES, NATIONS, SEAS, TOWNS, HAVENS, MOUNTAINS, RIVERS, DISTANCES, AND PEOPLES WHO NOW EXIST OR FORMERLY EXISTED.
John Bostock translation
The Caspian and the Hyrcanian Seas are generally looked upon as identical, but we find them again distinguished by Pliny in B. vi. c. 13, where he says that this inland sea commences to be called the Caspian after you have passed the river Cyrus (or Kúr), and that the Caspii live near it; and in C. 16, that it is called the Hyrcanian Sea, from the Hyrcani who live along its shores. The western side would therefore in strictness be called the Caspian, and the eastern the Hyrcanian Sea.