Walter W. Dalquest

Pleistocene Mammals from Aguascalientes, Central Mexico

Hundreds of fossils of middle Pleistocene age mammals have been obtained from the tufa, sands, and gravels of the Tacubaya Formation just east of the City of Aguascalientes, in central Mexico. The fossils are probably of Illinoian age. This is the only large, systematically-collected, local fauna known from the Pleistocene of Mexico. Few remains of small mammals were found, but the Cedazo local fauna includes at least 39 species, three here described as new. The Cedazo local fauna is a unit fauna, representing the kinds of mammals that lived together in one small area during one period of time. The Cedazo local fauna lived on plains or grasslands with brush and trees along watercourses but with no tropical forest element in the environment.

The Origin of the Mima Mounds of Western Washington

The Mima mounds occur on certain prairies of glacial outwash in western Washington. The mounds are closely spaced, round or oval, from 10 to 40 feet in diameter, and from 1 to 7 feet in height. The typical mound is a double-convex lens of loose, unstratified, black silt-gravel set in a shallow pit in stratified yellow outwash gravel. Mounds are found only where a thin layer of soil overlies a compact bed of gravel, not on deep prairie soils. The Mima mounds are formed by pocket gophers (Thomomys talpoides) over long periods of time. Gopher activity in any particular place destined to become a mound site starts with intensive burrowing, such as that required in the construction of a nest, which loosens the soil and stimulates the growth of vegetation. The vegetation, in turn, furnishes food for the gophers and encourages them to concentrate their activities in the vicinity. A stage is reached where the gophers find sufficient food on the mounds to maintain them the year around, making it unnecessary for them to forage, except at rare intervals, into the intermound depressions. In deep burrowing to create living quarters gophers dig a shallow pit in the stratified gravel beneath each mound. The smaller elements in the stratified gravel removed by deep burrowing become mixed with silt to form the substance of the mound lens. Stones too large to be moved by the gophers are undermined and settle to the bottom of the mound. In shallow exploratory burrowing in the peripheral zone the gophers do not undermine large stones but remove soil from about them, eventually leaving them exposed on the surface of the ground.

Early Blancan Mammals of the Beck Ranch Local Fauna of Texas

The Beck Ranch local fauna was recovered from 65 tons of sand and clay sediments from a quagmire in Scurry County, Texas. Of the 58 taxa identified, members of the genera Perognathus, Peromyscus, Nasua and Spilogale (?) are described as new species; Lasionycteris and Nasua are recorded from the Blancan age of North America for the first time; and the characters of Brachyopsigale dubius Hibbard are reassessed. The Beck Ranch local fauna is rich in small forms but larger mammals, other than Nannippus beckensis , are rare. The local fauna is thought to be younger than the Fox Canyon local fauna of Kansas, but slightly older than the Rexroad local fauna of Kansas, the Benson local fauna of Arizona, and the Blanco local fauna of Texas.

MAMMALS OF NORTH-CENTRAL TEXAS

North-central Texas includes five counties along the central part of the northern border of Texas. Of the 66 kinds of mammals recorded, 59 are native species and more than a third of these find their eastern or western limits of range in the area. Eastern woodland forms occupy the eastern part of the area, and Great Plains kinds the western. The Red River permits migration of both eastern and western species. Some westward immigration of eastern mammals has occurred in recent years. North-central Texas, as here defined, includes five counties that extend eastward from the eastern base of the Texas Panhandle along the Red River and make up approximately the central third of the northern border of the state. The counties, from west to east, are: Hardeman, Wilbarger, Wichita, Clay, and Montague. The area is 150 miles from west to east and averages about 30 miles from north to south. Elements of two distinct mammalian faunas meet in north-central Texas. The land west of Hardeman County is semiarid grassland and brushland and possesses a mammalian fauna typical of the Great Plains. From Montague County eastward the land is wooded and the mammals there are more typical of the woodlands of southeastern United States. From Hardeman County to Montague County the en- vironment is transitional and there is also a transition from a fauna typical of the Great Plains to a fauna of the southeastern woodlands. Many species of mammals range completely across north-central Texas. However, more than one third of the 59 full species of native mammals here listed find their eastern or western limit of range in the five-county area here considered. The woodland vole, for example, ex- tends no farther west than Montague County, and the northern grass- hopper mouse ranges no farther east than Wichita County. Neither of these species seems to have an ecological counterpart in the opposite fauna. The eastern woodrat and the southern plains woodrat meet in Clay and Montague counties. The ranges of these two species may overlap slightly but the animals are otherwise allopatric, and doubt- less they are ecological competitors.

Natural History of the Vampire Bats of Eastern Mexico

Vampire bats of two species range throughout eastern Mexico from the southern limits of the republic northward to approximately 175 miles from the United States boundary. The common vampire, Desmodus rotundus murinus Wagner, is a common to abundant bat almost wherever it is found. The hairy-legged vampire, Diphylla ecaudata centralis Thomas, is one of the rarer North American bats but seems to reach its maximum abundance in eastern Mexico. These disgusting but nevertheless interesting mammals do great damage to livestock and attack human beings on occasions. Domestic animals are weakened and sometimes die from loss of blood from the wounds inflicted by vampires, while the open wounds are a common site of infection by bacteria and parasitic insect larvae such as screw worms. Vampires are potential vectors of disease also. They are known to transmit rabies and some cattle diseases in Panama, Trinidad, and South America, and such communicable diseases as the hoof-and-mouth disease might easily be spread by vampires. In the British West Indies an intensive campaign has been carried out in an effort to rid the island of Trinidad of these da-igerous animals; The writer is convinced that a similar campaign must soon be undertaken in Mexico. The following report, which may assist in such a campaign, is based on several years of field work in eastern Mexico, during which period approximately ten thousand vampires were examined. In the uninhabited jungles of extreme southern Veracruz I found no vampires, although conditions, except for the absence of domestic animals, seemed to be ideal for these bats. Along the Rio Coatzacoalcos, at the northern edge of the uninhabited area, where people, horses, cattle and burros are again found, vampires again were encountered. Large game animals are abundant in the uninhabited area, but none of the many specimens taken showed evidence of vampire predation. Probably vampires were rare to uncommon in eastern Mexico in prehistoric times, but the arrival of domestic animals accompanying the conquest of the country by Europeans presented the existing vampires with a constantly increasing food supply in the relatively helpless burros, horses, and cattle. The common vampire breeds throughout the year, is extremely shy, is probably safe from most predators in the caves, it inhabits, is remarkably hardy, and has now increased in numbers until it is one of the commonest and most widespread mammals in eastern Mexico. It is adaptable enough to live in hollow trees and the structures of man and to live on the arid deserts as well as in the tropics. It is principally, perhaps almost entirely, dependent on domestic animals for food at the present time and may even attack man.

The Biology of the Least Shrew-Mole, Neurotrichus gibbsii Minor

The life history and economic status of four of the five genera of North American moles have been studied extensively by a number of workers, and literature on the subjects is voluminous. The genus Neurotrichus, however, the smallest and least fossorial of the American Talpidae, has been almost totally neglected in this respect. We find but four papers dealing with the habits of the shrew-mole: a short paper by Racey (1929), and several paragraphs in general works by Jackson (1915), Taylor and Shaw (1927), and by Bailey (1936). The present report serves to expand the knowledge of the biology of American moles and to place on record a number of unreported facts about Neurotrichus.

NOTES ON DIPODOMYS ELATOR, A RARE KANGAROO RAT

Dipodomys elator has proved one of the most elusive of American mammals. The species seems confined to 6 counties in north-central Texas and southern Oklahoma. It occupies mesquite scrubland, where other kinds of kangaroo rats would not be expected to occur. The nearest relative of D. elator seems to be D. ornatus of the central Mexican plateau, another rare species. These 2 species should be grouped together in an elator group. It is possible that other kinds of kangaroo rats of this group remain to be discovered in Texas and Mexico.

The Pleistocene Horse, Equus conversidens

Fossilized remains of small horses recently found near Canyon and Slaton, Texas, are referable to the Pleistocene species, Equus conversidens Owen, described from the Valley of Mexico in 1869. Fossils include a skull with articulated lower jaw and front limbs and referred lower jaws and front and back leg bones. Five nominal species are re- garded as synonyms of E. conversidens. The species is now known from Mexico, Texas, Arizona, New Mexico, Oklahoma, Kansas and Florida, from deposits of Yarmouthian to Wisconsin age. Fossilized remains of small horses are rather common in Pleistocene

MAMMALS OF THE PLEISTOCENE SLATON LOCAL FAUNA OF TEXAS

Reinvestigation, including washing of matrix, in the old Slaton quarry, Lubbock County, Texas, yielded remains of 30 kinds of mammals. A white- tailed prairie-dog, Cynomys vetus, is reported from Texas for the first time. Numer- ous good specimens of the extinct water rat. Neofiber leonardi, show the distinctness of that species. Abundant material permits detailed description of two extinct species of horses. The vertebrate fauna indicates a mild climate with extensive grasslands and scattered trees and thickets in the vicinity of the fossil site. The fauna is prob- ably of early Illinoian age. The Slaton quarry, source of the Slaton local fauna, is located on the north side of Yellowhouse Canyon, approximately five miles north of Slaton, Lubbock County, Texas. Johnson and Savage (1955) credit Mr. Porter Montgomery with the original discovery of vertebrate fossils at the site, then known as the Smart Ranch, in 1941. Grayson E. Meade collected fossils in the gray Pleistocene clays of the old lake bed in 1942, for the West Texas Museum, at Lubbock, and the Texas Bureau of Economic Geology, in Austin. Meade recognized the unique nature of the fauna and described an antilocaprid (1942) and a water rat (1952) from the locality. In the latter publication he formally named the Slaton local fauna. Evans and Meade (1945) gave a brief account of the Pleistocene deposits that yielded the Slaton local fauna, and a faunal list. The Slaton local fauna has been mentioned in print from time to time (eg. Hibbard, 1958) but no detailed account of the vertebrate fauna has been published. Meades account of the water rat from the Slaton quarry, a species otherwise unreported from the Pleistocene of Texas, stimulated a reexamination of the site during 1963 and 1964. The old Smart Ranch is now the property of Mr. Allen Wallace, and I am deeply grateful to Mr. Wallace for access to the deposits, the use of his power machinery in some of the excavating, and other favors. With the aid of tractors we were able to uncover some rich fossiliferous deposits, and 13 tons of gray clay matrix were removed to Wichita Falls and washed and sorted to obtain the microfossils present. The clay matrix is extremely fossiliferous. When washed through ordinary fly screen, the retained solids are mostly fossils. Most of the fossils are of plants and mollusk shells. Chips and bits of bones of large mammals are common, while remains of reptiles, amphibians, birds and small mammals are rare.

A New Pleistocene Local Fauna from Motley County, Texas

In the late fall of 1958, Mr. Gene Wilson of Ringgold, Texas, brought to Midwestern University some teeth of an extinct camel that he had found in the bed of a small arroyo tributary to Quitaque Creek, in the northeastern corner of Motley County. This locality is at the base of the Texas Panhandle, approximately 135 miles west of Wichita Falls. Mr. Wilson showed me where he had found the teeth, and much of the skull of the camel was recovered. On subsequent visits to the area additional vertebrate fossils were found, and a ton of gray clay matrix was washed and sorted (Hibbard, 1949) to recover the fossils of mollusks and small vertebrates. The kinds of animals identified from the site con-