Complex sentence: The thorax or pereon is smooth or slightly sculptured and sometimes spinose or rugose, with a flexion between it and the abdomen or pleon, so that from a lateral view, the front part of the animal is arched up.
Split into simpler sentences: The thorax or pereon is smooth or slightly sculptured and sometimes spinose or rugose. There is a flexion between it and the abdomen or pleon so that from a lateral view the front part of the animal is arched up.