rjlUS. COWIP. ZOOL APRo U HARVARD GAMBUSIA HETEROCHIR. A NEW POECILIID FISH Fi o?IHlV£RSlTl TEXAS, WITH AN ACCOUNT OF ITS HYBRIDIZATION"^""" WITH G. AFFINIS CLARK HUBBS, Department of Zoology, The University of Texas, Austin. Texas During the past decade a number of fishes have been described from Texas fresh-waters. Some of them have been known for years, but were not described until recently. Others, such as the new species of Gainbus:a described below, have not been recognized until recently. This new mosquitofish, apparently restricted to the headwaters of Clear Creek, Menard County, Texas, is separated by some 800 miles from the ranges of its nearest relatives. Many hybrids between this species and Gaynbitsia affinis ( Baird and Girard ) have been collected. The geographic distribution and morphologic variation of the hybrids is discussed. Material of the new species has been collected by the author, W. Gordon Craig, Theodosius Dobzhansky, Alvin E. Ellington, Sr., James D. French, Murray K. Muston, Kirk Strawn, and John E. Tilton. I also w.sh to thank Charles Wilkinson and H. Leslie Jones for per-mifsion to collect on their ranches. Dr. Billie L. Turner identified the plants. Mr. George G. Henderson, Jr., made the photographs. Miss Nancy Walker and Mrs. Jane Hubby made the drawings. Counts and measurements were made as detailed in Carl L. Hubbs and Lagler (1947). Names for gonopodial structures follow those g'ven by Carl L. Hubbs (1926). The schematic diagrams to deter-mine degree of hybridization are modified from those proposed by Anderson ( 1949). GAMBUSIA HETEROCHIR, sp. nov. Fig. 1 Material. — The type material consists of the 24.5 mm holotype (University of Michigan Museum of Zoology No. 170936) and 125 other specimens of 17 to 45 mm (UMMZ No. 170937, Stanford Uni-versity Nos. 46445 to 46451, United States National Museum No. 164573, Museum of Comparative Zoology, Harvard University No. 39684. Chicago Natural History Museum No. 61805, and Texas Nat-ural History Collection Nos. 3065 and 4652), all of which were seined on two occasions from the headspring of Clear Creek, Menard County, Texas, 10.4 miles west of Menard. The first of these collections was made on February 22, 1953, and the second on February 20, 1956. Many hybrids with G. affinis occur in both collections. Possibly some or all of the specimens designated as G. heterochir contain some genes from G. affinis. However, as introgression into G. heterochir appears to be uncommon and suspected hybrids are excluded from G. heterochir collections, I believe that most of the specimens con-sidered to be G. heterochir are not contaminated with G. affinis genes. Diagnosis. — A stocky species of Gambusia. The deep indentation on the upper margin of the male pectoral fin ( fig. 5 ) distinguishes
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