The Collaborative International Dictionary
Atrocha
Atrocha \At`ro*cha\, n. [NL., fr. Gr. 'a priv. + ? a circle.] (Zo["o]l.) A kind of ch[ae]topod larva in which no circles of cilia are developed.
Wiktionary
atrocha
n. (context zoology English) A kind of chaetopod larva in which no circles of cilium are developed.