The sub-genus Chasmops of the genus Phacops is so rarely, if ever, found in great Britain, except as disconnected heads and pygidia, that a specimen which shows the cephalic shield attached to several thoracio rings deserves notice.
The two British species recognised by Salter (omitting the doubtful Ch. Jukesii) are Ch. macroura (Sjogren) and Ch. conophthalmus (Boeck?), but he apparently perceived that more than two species were included under these names (Mon. Brit. Tril. p. 38).