From GPO access (e-CFR Data is current as of October 13, 2011 ):

Title 43: Public Lands: Interior
PART 3620—FREE USE OF PETRIFIED WOOD
Subpart 3622—Free Use of Petrified Wood
§ 3622.1 Program: General.
(a) Persons may collect limited quantities of petrified wood for noncommercial purposes under terms and conditions consistent with the preservation of significant deposits as a public recreational resource.
(b) The purchase of petrified wood for commercial purposes is provided for in §3602.10 et seq. of this chapter.

§ 3622.2 Procedures; permits.
No application or permit for free use is required except for specimens over 250 pounds in weight. The authorized officer may issue permits, using the procedures of subpart 3604 of this chapter, for the removal of such specimens if the applicant certifies that they will be displayed to the public in a museum or similar institution.
(a) All public lands administered by the Bureau of Land Management and the Bureau of Reclamation are open to or available for free use removal of petrified wood unless otherwise provided for by notice in theFederal Register.Free use areas under the jurisdiction of said Bureaus may be modified or cancelled by notices published in theFederal Register.
(b) The heads of other Bureaus in the Department of the Interior may publish in the Federal Register designations, modifications or cancellations of free use areas for petrified wood on lands under their jurisdiction.

§ 3622.4 Collection rules.
(1) The maximum quantity of petrified wood that any one person is allowed to remove without charge per day is 25 pounds in weight plus one piece, provided that the maximum total amount that one person may remove in one calendar year shall not exceed 250 pounds. Pooling of quotas to obtain pieces larger than 250 pounds is not allowed.
(2) Except for holders of permits issued under subpart 3604 of this chapter to remove museum pieces, no person shall use explosives, power equipment, including, but not limited to, tractors, bulldozers, plows, power-shovels, semi-trailers or other heavy equipment for the excavation or removal of petrified wood.
(3) Petrified wood obtained under this section shall be for personal use and shall not be sold or bartered to commercial dealers.
The collection of petrified wood shall be accomplished in a manner that prevents hazards to public health and safety, and minimizes and mitigates environmental damage.

Reasonable Amounts may be defined by each field office for:
Decorative Rock (for example, a wheel barrow full per year)
Mineral specimens (for example, a five gallon bucket full per year)
Petrified Wood (for example, 25 pounds per day plus one rock and 250 pounds per year)
Common Invertebrate and Plant Fossils (for example, a five gallon bucket full per year)
Amounts beyond “a reasonable amount” would require a permit.

From the Bureau of Land Management
The OPLMA-PRP provides for casual collecting of reasonable amounts of common invertebrate and plant fossils from public lands for personal use without a permit.
Casual collecting as defined in 16 U.S.C. 470aaa(1) means:
“… the collecting of a reasonable amount of common invertebrate and plant paleontological resources for non-commercial personal use, either by surface collection or the use of non-powered hand tools resulting in only negligible disturbance to the Earth’s surface and other resources.”
Commercial collection of any type of fossil from Federal lands is not allowed, except for petrified wood which was designated a mineral material by Congress in 1962, and therefore, is salable under the Mineral Materials Act (43 CFR 3600.)

What are Fossils?
Paleontological resources (fossils, tracks, fossilized wood) are the remains or traces of plants and animals that lived during periods of Earth’s history. Fossils are unique, non-renewable resources that provide clues to the history of life on earth, and many are considered to have important scientific value.

Hobbyists May Collect Some Fossils for Personal Use
Most BLM managed public lands are open to exploring and hobby collecting, but some areas are managed with special restrictions to protect their natural and cultural resources. Collecting and access may be limited in these areas. Contact the SGFO to find out about areas where fossil collecting is limited.

Collection Etiquette
Fossil collecting activities that damage the public lands and resources, or that make them dangerous for others, are not permitted. Uprooting large areas of grass, sagebrush, and other plants, or digging large holes, may create hazardous conditions and can contribute to erosion. An archaeological site might even be damaged or destroyed and this is prohibited by the Archaeological Resources Protection Act of 1979. Many fossil specimens are found right on the surface, and digging is often unnecessary.

Invertebrate and Plant Fossils
Invertebrates are animals without backbones, such as clams, snails, ammonites, trilobites and corals. Common invertebrate and plant fossils may be collected in reasonable quantities for personal use, but they cannot be traded, bartered or sold to anyone else.
Commercial collecting of invertebrate and plant fossils from public lands is not allowed. Over-collecting of invertebrates that once were common has made some of them difficult to find. Please remember to leave something for your children and grandchildren to enjoy!

Vertebrate Fossils
Vertebrates include sharks and other fish, dinosaurs, turtles, mammals – in fact, any animal with a skeleton of cartilage or bone. Because vertebrae fossils are rare and scientifically important, they may be collected only after obtaining a permit from the BLM’s State Office.

Private Land
Contact landowners for permission before you collect on private land. Your local BLM office sells maps that show public, private and other lands, and roads that provide access to public lands. Always respect private property rights.

PART 8340—OFF-ROAD VEHICLES
The operation of off-road vehicles is permitted on those areas and trails designated as open to off-road vehicle use.
(f) No person shall operate an off-road vehicle on public lands:
(1) In a reckless, careless, or negligent manner;
(2) In excess of established speed limits;
(3) While under the influence of alcohol, narcotics, or dangerous drugs;
(4) In a manner causing, or likely to cause significant, undue damage to or disturbance of the soil, wildlife, wildlife habitat, improvements, cultural, or vegetative resources or other authorized uses of the public lands
(5) During night hours, from a half-hour after sunset to a half-hour before sunrise, without lighted headlights and taillights.
(g) Drivers of off-road vehicles shall yield the right-of-way to pedestrians, saddle horses, pack trains, and animal-drawn vehicles.