Seventeen volunteers appeared in the Day’s Inn parking lot at 7:30 on Saturday morning,  April 16, to continue excavation at the Tarkio Valley Megalonyx site. Work resumed Sunday morning and continued until noon. First, the water that had collected behind the coffer dam was bailed by bucket brigade leaving only that in the sump. This task was completed within 30 minutes. The sticky residue from the protective layer was then removed by shovel and bucket over the next hour. Excavation continued to the North of the January trench. The floor of the January trench was covered with muck deposited by the West Tarkio between the January excavation and construction of the coffer dam. The difference in lithology between this and the sloth-bearing deposit provided a distinct boundary between the old and new excavations. 
 
It is impossible to evaluate the degree of reworking at this time. On the same level, bone began to appear immediately to both the north and to the east of the January trench. A jumble of fractured bone to the east was carefully cleaned of matrix and by the end of the day was identified as part of the pelvis including an acetabulum. The north end of this cluster was 3’ 3” north of the east datum stake and the south end was 1’ 5” inches north of the same datum. The pelvis fragments were in a 2’ x 3’ cluster with the west side rested against the east wall of the January trench. The top of the pelvis was 5” above datum The crew spread out over the floor of the pit left by the excavator and began shoveling down to sloth level. A gravel deposit in the north central area of the clearing was encountered immediately. This clearly was entrenched into the blue-grey clay matrix containing the sloth. Unfortunately, the distal end of a Megalonyx radius and a carpal/tarsal were encountered in this unit demonstrating some specimen reworking in late glacial or early Holocene time. The bone cluster extended down to 6 “ below datum, the acetabulum was 3” below datum. This specimen was covered with sand bags for recovery later in the month. 
 
Another cluster of bones was discovered immediately north of the northeast corner of the January trench wall. This cluster was offset 2 feet northwest of the pelvis cluster and was at the same elevation. This cluster contained a humerus next to the trench wall and extended four feet north to a sub-cluster of three ribs. One or more mandibles, a rib and, potentially, a major portion of the skull were in between the two. All were removed in one of three plaster casts. These ranged in depth between minus 4 and plus 7 inches with respect to datum. 
 
During this excavation, it was noted that the fossil layer ranged between a few inches above and below datum while the bone layer was recorded as between 17 and 28 inches below datum in January. A question for the next trip will be to test for the possibility of two sloth layers, greater topographic relief or measurement error to explain this discrepancy.   
 
Participants for one or both days were, in order of sign in, Don Wirth, Sonya Housholder, Rosemary Harding, Gene Turner, Larry Pierson (dad), Garrett Pierson (son), Robert McAfee, John McLure, Georgia Krauss, Aaron Last, Sara Laue, Pat McCauley, Charlotte 
Wright, Chuck McKee, Melissa Mott (daughter), William Mott (dad), Lynette Stephenson, David Brenzel and Holmes Semken. 
 
 
Next weekend, April 24, David and Holmes will give the sloth talk at the Cedar Valley Rock and Mineral Show in Cedar Rapids. The next trip to Northboro is scheduled for the weekend of April 30. 
 
Holmes A. Semken, Jr., April 22, 2004 (edited April 29).