14 -NOTES ON THE FRESH-WATER SPECIES OF SAN THIS OBISPO COUNTY, 
CALIFORNIA. 
By DAVID STARR JORDAN. 
The county of San Luis Obispo lies along the coast of California, midway between 
Monterey and Santa Barbara. It is composed of two or three isolated valleys opening- 
out to the sea, and surrounded on all sides by high and barren mountains. These 
mountains have served as a barrier, shutting- off all access of fishes to the streams of 
the region from the larger basins of the north and east. The valleys of San Luis 
Obispo are traversed by clear, swift, cold streams rising in mountain springs. In these 
streams very few species of fishes are found, and these few, except in one case {Agosia 
nuhila), are species which have come into the fresh Avaters by Avay of the sea. None of 
the characteristic types of the San Joaquin and Sacramento valleys are found in San 
Luis Obispo County. This is evidently not due to any character of the Avaters, but 
simply to the fact that these fishes can not reach San Luis Obispo except by descent 
to the sea. The extreme paucity of species of fishes becomes a fact of some interest in 
connection Avith geographic distribution. In the investigations of these streams I 
received the efficient assistance of Mr. J. F. West, of Paso Eobles. 
The streams examined Avere San Luis Creek, Corral de Piedra Creek, and Arroyo 
Grande. 
San Luis Greeh is a clear, cold, swift stream Avhich drains the valley of San Luis 
Obispo. It Avas examined near Avila, AA-here it is deep and tortuous, Avith high banks 
covered -with tangled Amgetation. Here the following species Avere seen: 
1. Agosia nubila (Girard). lo springs amoug watercressos, rather common. A Amry widely distrib- 
uted species, found in all springs of the Coast Range, northward. The California specimens 
may represent a distinct subspecies, but the characters need further comparison. 
2. Cottus gulosus (Girard). Abundant and large. 
3. Eucyclogobius newberrii (Girard). Common in the bottom of the stream, in quiet places. 
4. Gasterosteus microcephalus Girard. EAmrywhere common, especially in pools away from the 
current and amoug Aveeds. 
Corral de Piedra Creel; is a clear, cold brook AAdth muddy bottom, full of chara, 
Avatercress, and other plants, and reduced in summer to a succession of pools. It 
tioAA s into a larger stream, Pismo Creek, AA'hich in turn runs into Arroyo Grande near 
its mouth on Pismo Beach. Here Avas found but one species, the stickleback. Caster- 
osteus microcephalus Girard, AA^hich Avas very common. 
Arroyo Grande is a large stream, clear, cold, and rather shalloAV. It runs swiftly 
over a gravelly bottom. About the village of Arroyo Grande no fislies Avere seen. 
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