I n my last communication, of March 1864, I described all the fossils then known from the Lower Lingula-flags of Pembrokeshire. There are now several more forms to communicate, some of which are generically new, and others are new species of old and well-known genera. I must confine myself in this paper to one or two species of which a better knowledge has been obtained, and the description of which it is desirable to amend, as the forms differ in some marked peculiarities from any of the Trilobite-group hitherto described. The new genus Anopolenus (see vol. xx. p. 36) was supposed, and with good reason, to be a blind Trilobite allied to Paradoxides , without facial sutures or head-spines, and with truncate body-segments not produced into spinous appendages as in most of its congeners (see pl. xiii. of the vol. above quoted, figs. 4, 5). All this was true so far as I then had materials; but the subjoined description, by my friend Mr. Hicks, of a new species of the genus will show that I then only had a part either of head or body of this curious animal, which turns out to be more truly intermediate between Paradoxides and Olenus than was before supposed, while it also presents characters contradictory to those of either genus. It possesses eyes, facial suture, and expanded pleuræ; but the arrangement of these is abnormal, as Mr. Hicks's description will show. Before giving his description of them, however, I would call the attention of the