Complex sentence: The top of the cephalothorax is covered by a carapace, that of jumping spiders has a distinctive rectangular shape, and that of the genus "Portia" slopes gently upward almost to the back, then steeply down.
Split into simpler sentences: The top of the cephalothorax is covered by a carapace. In the genus "Portia", the carapace slopes gently upward almost to the back, then steeply down.