– 16 – G and later type PMS stars can be distinguished from AGB stars by the presence of emission lines associated with chromospheric activity and/or accretion. H α (6562 ˚ A) and the Ca II infrared triplet (8498, 8542, 8662 ˚ A) are the most conspicuous of such lines. The Li I 6707 ˚ A absorption line is also a very good indicator of stellar youth in mid-K to M-type stars because Li is burned very efficiently in the convective interiors of low-mass stars and is depleted soon after these objects arrive on the main-sequence. In Table 2, we tabulate the velocity dispersion of the H α emission lines, the equivalent widths of the detected Li I 6707 ˚ A absorption lines, and the identification of the Ca II infrared triplets. After removing the Be star from consideration, we detect H α emission in 25 of our targets. All of them exhibit Li I absorption and/or Ca II emission and can therefore be considered bona fide PMS stars. Six of the targets exhibit H α absorption. All of them are M-type stars with small 24 µ m excesses and no evidence for Li I absorption nor Ca II emission. Since these targets are most likely background AGB stars, we do not include them in our sample of transition disks. Two of our targets, objects # 12 and 22, show no evidence for H α emission or absorption. Object #12 is the well studied K-type PMS star Do Ar 21, and we thus include it in our transition disks sample. Object # 22 is a M6 star with small 24 µ m excesses and no evidence for Li I absorption nor Ca II emission and is also a likely AGB star. To sum up, after removing one classical Be star (object # 2) and seven likely AGB stars (objects # 4, 6, 8, 10, 22, 33, 34), we are left with 26 bona-fide PMS stars. These 26 objects constitute our sample of transition disks. As shown in Figure 1, all the contaminating objects have [3.6]-[24] ≲ 2.5, while 24 of the 26 PMS stars have [3.6]-[24] ≳ 2.5. This result underscores the need for spectroscopic diagnostics to firmly establish the PMS sequence status of Spitzer -selected YSO candidates, especially those with small IR excesses.