1 84 CARL L. HUBBS. 



along the rock-bound portions of the central California coast, 

 its habitat differing widely from that usual to the . species of 

 the family, most of which live in the surf along sandy beaches, 

 or in sheltered bays. In the preference of this species for this 

 extreme type of habitat it is perhaps most nearly approached by 

 Micrometrus minimus. The associational distribution of even 

 these two species is, however, imperfectly complementary. Both 

 range from the region of San Francisco southward in the cold 

 coastal waters of central California to the reefs about Point 

 Conception, where the habitat of A. aurora is abruptly terminated, 

 whereas that of M. miniums is continued southward in the rela- 

 tively warm waters along the coasts of southern and of Lower 

 California. Micrometrus minimus is in fact most abundant in 

 the warmer southern portion of its range, although fairly com- 

 mon northward, where the ranges of the two species coincide. 

 Here, however, M. minimus occupies to a large extent a biotic 

 association different from that of its congener, but adjacent to 

 it : it lives and breeds in or not far below the lowermost tide- 

 levels, mostly in the low, deep, plant-filled pools of the reefs (but 

 also in enclosed bays and estcros}. Amphigonopterus aurora, in 

 contrast, is restricted to the reefs, and while breeding at times 

 even in the same pools with its relative, more commonly lives and 

 breeds in the pools and channels of medium tidal height, particu- 

 larly those that are largely open, free of eel-grass and algse, and 

 floored with sand. The breeding season of Amphigonopterus, 

 moreover, appears to begin earlier than that of Micrometrus in 

 central California (see following section). Both of these fishes 

 were found associated in the lower outer rock-pools of the Cali- 

 fornia reefs with the following other species of the family : Em- 

 biotoca jacksoni, E. latcralis, Hypsurus caryi and Cymatogastcr 

 aggregatus. 



In these open pools the fishes of this species swim about freely 

 in schools 1 at low-tide, occupying the mid-water stratum chiefly, 



1 That these schools of A. aurora remain intact for considerable periods of 

 time appears probable from two sets of observations. A number of pools on 

 the reefs just south of Piedras Blancas, and just south of Pt. Sal, by careful 

 observation over a period of several days (during a single series of low-tides 

 in each case), were found to contain many more individuals than any of the 

 adjoining pools, and to contain schools of apparently the same individuals, 



