Okay, trudging through that dissertation....
It looks like there are a couple steps, based on body morphology, to determine whether the fish is a Centropyge or Paracentropyge (or a Xiphypops).
Step 1: What kind of spines does your fish have around its eyes?
A) One to three stout spines on ventral margin of preorbital (lacrymal), pointing ventroposteriorly to posteriorly, their length at least one-third to one-half the diameter ofthe orbit, with or without an additional series of smaller spines or spinules on the exposed preorbital margin; maximum size not exceeding 60 mm SL (rarely exceeding 55 mm SL); body depth 1.8-2.3 (usually more than 2) in SL
Congrats! It's Centropyge, sub-genus: Xiphypops. Stop here, do not proceed to Step 2.
B) Spines or spinules on the ventral or posterior margins of the preorbital present or absent, but when present, none exceed one-third diameter of orbit; maximum size exceeding 60 mm SL; body depth 1.5-2.2 (usually less than 2) in SL
Well, it's EITHER sub-genus Centropyge OR Paracentropyge. To find out which, proceed to Step 2.
Step 2: What kind of body and/or dorsal spines does your fish have?
A) Body depth less than 1.9 (usually less than 1.8) in SL; XIII dorsal spines, body with alternating dark and pale bars; OR XIV dorsal spines, body color purplish blue dorsoposteriorly and with a purplish blue triangular patch from interorbital to axis of pectoral fin to origin of dorsal fin, yellow ventrally and anteriorly on head ->
Congrats, it's a sub-genus Paracentropyge!
B) Body depth 1.6-2.2 (usually 1.8-2.0) in SL; XIII-XVI (usually XIV-XV) dorsal spines; color variable depending on species, but not as described in 2a ->
Congrats, it's a sub-genus Centropyge!
*****
Note that sub-genus Centropyge seems to be defined primarily on the basis of exclusion: if it's NOT Xiphypops or Paracentropyge, then it's automatically Centropyge by default.
According to the dissertation, the Colini and Narcosis both belong to the "colini" complex of the Centropyge sub-genus, which he defines as follows:
"colini" complex (two species: colini and narcosis); similar in some respects to the "aurantia" complex [e.g., relatively deep body (depth 1.66-1.84 in SL),
5) reduced number o f gill rakers (14-18), steep and relatively straight head profile, and some aspects of behavior and ecology], but differing in general body color (pale yellow with a bright yellow spot on each scale, thin blue margin around eye) and more rounded shape ofposterior soft: portions of dorsal and anal fins (caudal fin extending posteriorly without forming a more or less continuous arc with the soft: portions of dorsal and anal fins);
He also notes - which matches your observations! - that the "colini" complex shares similarities with the Paracentropyge species:
Ofthe four complexes, the "aurantia" complex and the "colini" complex share with Paracentropyge a deeper body (depth 1.46-1.90 in SL for Paracentropyge, compared with 1.63-1.85 for the combined two complexes). They also share with Paracentropyge a tendency for more cryptic dwelling habits.
