cephalothorax
Concise Oxford English Dictionary © 2008 Oxford University Press:
cephalothorax /ˌsɛf(ə)ləʊˈθɔːraks, ˌkɛf-/
▶noun (pl. cephalothoraces /-ˈθɔːrəsiːz/ or cephalothoraxes) Zoology the fused head and thorax of spiders and other chelicerate arthropods.
'cephalothorax' also found in these Oxford entries:

