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382 Robert Rush Miller exotics as Gambusia a. afinis, Micropterus salmoides, and the still persistent carp. Cyprinodon latifasciatus Garman, Parras pupfish.-This distinc- tive species, like Stypodon signifer, once inhabited a spring or springs near Parras, Coahuila, Mexico. It occurred there in 1880 and at least until 1903, when George Hochderfer obtained 9 specimens (USNM 50970). It has not been taken since and is very likely extinct. The probable causes of its extermination are given above under the ac- count of Stypodon signif er. . Gambusia gaigei Hubbs, Big Bend gambusia.-This species was first discovered at Boquillas Spring, near the Rio Grande, Texas, in 1928, but became extinct there by 1954. It was more recently collected at Graham Ranch Warm Springs. There, in 1954, nearly 95 per cent of the population of Gambusia was G. gaigei, the remainder G. affinis; in 1956, however, the proportions were reversed, so that the known population of G. gaigei sank to a very, low level. The more widespread and aggressive mosquitofish, G. affcnis, had probably been introduced (Clark Hubbs and Springer, 1957, p. 305). The imminent danger of extinction of the Big Bend gambusia was subsequently relieved by action of the National Park Service, which eliminated the in- troduced species and stocked the native one in other springs. How- ever, on April 16, 1960, Clark Hubbs (in litt.) found the surviving population of G. gaigei to be very small since Rio Grande species, in- cluding G. affinis, had penetrated the waters reserved for the native species, which is unable to compete successfully with them. In a last-ditch attempt to save the Big Bend gambusia, Dr. Hubbs car- ried back to Austin more than half of the population. It was esti- mated by him that fewer than 24 individuals of the species existed and that the wild population would become extinct by midsummer, 1960. It is hoped that several hundred individuals may be reared from the brood stock returned to Austin and that Big Bend National Park may successfully be restocked. The species was prematurely reported to be extinct by Matthiessen (1959,p. 271). Gila crassicauda (Baird and Girard), thicktail chub.-This spe- cies, which reached a length of about I foot, formerly was common in lowland waters of the Central Valley of California (including Clear Lake and Coyote Creek, a southern tributary to San Francisco Bays) ; `The supposed occurrence of the species in Salinas River, tributary to Mon- terey Bay, is questionable (Clark Hubl@6 1947, p. 148). 11