(b) The parenthetical clause est enim . . . sepulcrorum explains collustrarem.

(c) in qua . . . cylindri is an adjectival clause enlarging columellam.

You may now translate into your best English, following closely the thought and the order of the Latin:—

Well, as I was surveying the whole place (there is a large number of tombs at[18] the Agrigentine gate) I perceived a small column just showing above the undergrowth, on which appeared the figure of a sphere and a cylinder.

[IV.] Atque ego statim Syracusanis—erant autem principes mecum—dixi me illud ipsum arbitrari esse, quod quaererem.

(i.) Vocabulary.—The words of this sentence present no difficulty.

(ii.) Translation.—With the practice you have now had, you may translate at once; but notice carefully that—

(a) the parenthetical clause erant . . . mecum enlarges Syracusanis; and

(b) quod quaererem describes illud ipsum.

So I immediately said to the Syracusans who were with me (some people of importance) that I thought that was the very thing I was looking for.