Scarab.
byways
Bellybuttons would be the longest word I can think of beginning with a 'b' and ending in an 's'.
Eight letter words beginning with b, ending with e:backsidebaselinebegrudgebelittleblockadeblockagebreakage
thumb
thumb
cherrub
Ballerina is one 9-letter word beginning with B and ending with A.
Some seven letter words starting with B are:bathtubdisturbperturbproverbrhubarbsuccumbtaxicabwashtub
baobab.
carob climb
Caleb fdhrsb
bath