Apple Inc.’s iPhone took 19.2 percent of the U.S. market for “smart” phones in the first quarter of 2008. Palm Inc., a pioneer in the category along with RIM, also picked up market share in the first quarter, when it grabbed 13.4 percent of smart phone sales, up from 7.9 percent in the fourth quarter. No. 4 in market share in the most recent quarter was Samsung Electronics, with 8.6 percent, up from 5.1 percent in the fourth quarter, a rise credited to the availability of the BlackJack on Verizon Wireless. Motorola Corp., which is struggling in the overall cell-phone market, did poorly in smart phones as well, dropping from a 7.5 percent share in the fourth quarter.