Fish Fauna of Johnston Is. — GOSLINE 
467 
Fig. 4. Diagram of the zoogeographic components making up the inshore fish fauna of Johnston Island and 
the island chains nearest to Johnston. A, that portion of the Line Island fauna that does not reach Johnston or 
the Hawaiian Islands; B, that portion of the Line Island fauna that reaches to Johnston but not to the Hawai- 
ian Islands; C, the component that is held in common by the Line Islands, Johnston, and the Hawaiian Islands; 
D, the component that is common to the Line and Hawaiian Islands but has not, up to now, been recorded 
from Johnston; E, that portion of the Hawaiian fauna that has reached Johnston but not farther south; F, the 
portion of the Hawaiian fauna that is restricted to the Hawaiian chain; and G, the component restricted to 
Johnston Island. Widths of the bars, except D, represent the relative strengths of the various components; for 
the way in which these widths were calculated, see text. 
Hawaii after hurdling the major one between 
Palmyra and Johnston is that the ecological 
conditions in Hawaii are not suitable to them. 
This is of course merely a guess, but it may 
be noted that the Johnston coral reefs, made 
up as they are to a considerable extent of 
Acropora , would seem to form a quite differ- 
ent environment from the Hawaiian reefs, 
where Acropora , amongst other elements, is 
lacking. To bulwark this point further it may 
be noted that certain rather prominent com- 
ponents of the tropical Pacific fauna that do 
reach Hawaii are rare there and apparently do 
not find the environment particularly suitable. 
In this category belong such species as Gym- 
nothorax pictus , Holocentrus microstomas, Thalas- 
soma lutescens , Chaetodon citrinellus , Chaetodon 
ephippium , Pomacanthus imperator , and Acan- 
thurus aliala . 
Summing up for the "northbound” fishes 
