Sentence:  This mixture was to be effected either by drawing the juries partly from the senate (of about 300 members), partly from an <WSD>"album</WSD>" of 300 "equites" (Plut. "CG" 5.2, "Comp." 2.1), or by adlecting 600 "equites" into the senate and drawing the juries from this new senatorial order (Liv. "Per." 60). 
Meaning of the word marked with <WSD> tags:  A collection, especially of literary items