Note 252 — Chapter V

V. 15. ἡ γὰρ πορφύρα περὶ ἔτη ἕξ, καὶ καθ’ ἕκαστον ἐνιαυτὸν φανερά ἐστιν ἡ αὔξησις τοῖς διαστήμασι τοῖς ἐν τῷ ὀστράκῳ τῆς ἕλικος. The translation above is taken from Professor D’Arcy Thompson (ibid.), to whose kindness I owe the following reference and much else in this chapter. Pliny, IX. 60, makes the Murex live seven years.