Lathwell produced some top- class shots, including one extraordinary stroke over midwicket for six off Darren Thomas with a minimum of back- lift.
There were eight fours in his 62-ball innings, ended by a fine diving catch at short midwicket by Matthew Maynard, off the first ball sent down by Tony Cottey.
Robert Croft and Cottey did their best to put the brake on Somerset, after the hosts had cruised to 124 for two off 19 overs. But, with time to play themselves in, Richard Harden (50 not out) and Peter Bowler (34 not out) put the result beyond doubt, taking few risks in a fifth-wicket stand of 84.
Glamorgan had lost the toss in heavily overcast conditions, and their openers Steve James and Hugh Morris were soon back in the pavilion, with only six runs on the board - all extras.
Adrian Dale (47) and Maynard (26) repaired the early damage, before Cottey produced a gem of an innings, making 61, including four fours and a six over midwicket off Keith Parsons.
Shivnarine Chanderpaul hit a superb century to lead West Indies to a 10-wicket win over India in their final one-day international. Chanderpaul hit 109 not out as the West Indies, replying to India's total of 199 for seven, reached their target without losing a wicket and with six overs to spare.
Fellow opener Stuart Williams supported Chanderpaul, who was named both man of the match and man of the series, with an unbeaten 78 as the West Indies, batting on a placid pitch, reached 200 without loss in 44.4 overs.
India had got off to a dreadful start after being put in to bat, losing Sachin Tendulkar for one and Saurav Ganguly for four.
The Indian innings was rescued from complete disaster by Ajay Jadeja, who made a fluent 68 off 78 balls, hitting four fours.
West Indies' captain Courtney Walsh was the most successful bowler with two for 26, including the prized scalp of Tendulkar, who was brilliantly caught at first slip by Brian Lara in the fifth over.
Curtly Ambrose, in his first over, took his 199th wicket in one-day internationals when he bowled Ganguly. Dravid and Azharuddin added 56 for the third wicket to revive the innings but both were dismissed as India crawled to 100. Jadeja and Singh featured in a fifth-wicket stand of 75 to bring a measure of respectability to India's total.
Walsh produced a perfect yorker to rip out Jadeja's middle stump with the first delivery of the 49th over. As Chanderpaul and Williams began clocking up the runs, it was soon clear that India's total would not be nearly enough.Reuse content