Match scores (SWALEC Stadium)
Somerset won by 170 runs
Somerset inns: 338-3 (Allenby 144*, Elgar 96, Hildreth 58*)
Glamorgan inns (36.4 overs): 168 (Carlson 63* van der Merwe 3-21)
Match report
A career best 144 not out from former Glamorgan player Jim Allenby ensured Somerset maintained their perfect start to the Royal London One Day Cup in Cardiff.
The Southern Group pacesetters easily defended a total of 338 for three as they recorded a 170-run victory and inflicted a third defeat in four games on Glamorgan.
Glamorgan elected to field after winning the toss and enjoyed some early success as Steven Davies' wretched form continued.
The opener had made three successive ducks coming into the game, and although he at least managed to get off the mark from a no ball, he missed a straight one from Marchant de Lange and was trapped lbw for four.
Peter Trego then offered Michael Hogan a return catch on 15 to leave Somerset 42 for two, but Allenby and Dean Elgar then settled in to a productive partnership of 187 in 33 overs.
Both batsmen reached their fifties in the same over, and Elgar was only four short of his second century in three games when he edged a catch down the leg side off Timm van der Gugten to wicketkeeper Chris Cooke.
After reaching his century, Allenby and James Hildreth staged a furious assault on the Glamorgan attack, with the latter striking an undefeated 58 from only 28 balls.
The fourth-wicket pair plundered 134 from the final 10 overs with Allenby finishing with six sixes and 11 fours, while De Lange, who had conceded only 38 from his first seven overs, was hammered for 55 in his final three.
Glamorgan soon lost openers David Lloyd and Jacques Rudolph, and when Colin Ingram was out in the 12th over for two, they had subsided to 27 for two.
Will Bragg and Kiran Carlson put on 55 for the fourth wicket to provide some resistance, but Bragg was stumped by Davies off a wide down the leg-side from Allenby for 32 and Aneurin Donald was bowled for 10 by Paul van Meekeren to leave the hosts five down with only 95 on the board.
Carlson drove powerfully through the off side to complete his half-century from 47 balls with six boundaries, but after scoring 63, his highest List A total, he perished attempting an expansive shot against Tim Groenewald's medium pace.
There was little resistance from the lower order, and when Van Der Gugten was caught on the midwicket boundary Glamorgan had been defeated by a substantial margin with 13.2 overs remaining.